The 6G72 engine, a 3.0-liter V6 used in Mitsubishi performance icons like the 3000GT VR-4, Dodge Stealth R/T Twin Turbo, and various other platforms, is a legend in the tuning world. Its cast-iron block and aluminum heads provide a stout foundation, but the stock exhaust system is a significant bottleneck, especially in twin-turbo configurations. Upgrading to a high-performance twin turbo exhaust system unleashes the engine's true potential by reducing back pressure, lowering exhaust gas temperatures (EGTs), and improving turbo spool time. The result is not only a substantial increase in horsepower and torque but also enhanced reliability under sustained boost. In this guide, we break down the top five 6G72 twin-turbo exhaust systems available today, covering what makes each one stand out in terms of power, sound, construction, and value.

How the Right Exhaust System Transforms Your 6G72 Twin Turbo

Before diving into specific products, it's crucial to understand why an aftermarket exhaust is one of the most effective upgrades for a forced-induction 6G72. The stock system was designed for a balance of noise compliance and cost, resulting in restrictive catalytic converters, crushed bends, and mufflers that create excessive back pressure. In a twin-turbo setup, high back pressure forces the turbos to work harder to push exhaust gases out, increasing heat soak and reducing efficiency. A properly designed aftermarket system uses mandrel-bent tubing, high-flow catalysts (or test pipes), and straight-through mufflers to dramatically drop back pressure. This allows the turbos to spool faster and more efficiently, leading to a broader powerband and lower EGTs, which is critical for preventing knock and pre-ignition under high boost. Many tuners report gains of 20-40 wheel horsepower on an otherwise stock 6G72 twin-turbo simply by swapping the cat-back or turbo-back exhaust.

1. Borla 140086 Exhaust System (Cat-Back)

The Borla 140086 is a frequent choice for 6G72 owners who demand uncompromising build quality and a signature aggressive sound without drone. This cat-back system is constructed from T-304 stainless steel, offering excellent corrosion resistance and longevity even in harsh climates. Borla uses a proprietary straight-through core design within its mufflers, which minimizes flow restriction while still managing sound levels effectively. The result is a deep, muscular tone that complements the twin-turbo induction noise without being obnoxious at highway speeds.

  • Construction: T-304 stainless steel, fully polished, with CNC-mandrel bends for smooth flow.
  • Design: Straight-through multi-core muffler technology ensures maximum exhaust velocity.
  • Installation: Precision laser-cut flanges and a direct-fit design mean no cutting or welding is required for most applications.
  • Performance: Users report noticeable seat-of-the-pants gains, especially in mid-range torque. Borla claims up to 10-15 HP improvement on a stock twin-turbo setup.
  • Warranty: Million-mile warranty underscores its durability.

The Borla 140086 is an ideal pick for someone who wants a premium, hassle-free upgrade that will outlast the car. Its sound is more refined than some competitors, making it suitable for daily drivers who want an assertive note without attracting unwanted attention.

2. MagnaFlow 16580 Exhaust System (Cat-Back)

MagnaFlow is synonymous with flow, and the 16580 system for the 6G72 twin-turbo lives up to that reputation. Like Borla, it uses 100% stainless steel construction, but MagnaFlow employs a baffled muffler design that uses a straight-through perforated core surrounded by acoustic packing material. This creates a deep, throaty tone that is slightly louder than the Borla but still very manageable. The mandrel-bent 2.5-inch tubing is sized perfectly for the 6G72's twin-turbo flow requirements, balancing scavenging with minimal back pressure.

  • Construction: Stainless steel throughout, with a mirror-like polished finish on the tip.
  • Design: Free-flowing, straight-through muffler with acoustic fiber packing to absorb high frequencies.
  • Installation: Bolt-on application with OE-style hangers. Some users note the tips may require minor adjustment to center perfectly in the bumper cutouts.
  • Performance: MagnaFlow claims gains of 10-18 horsepower and a noticeable improvement in throttle response. The reduced back pressure helps lower EGTs by 20-30°F in sustained pulls.
  • Warranty: Limited lifetime warranty to the original purchaser.

One standout feature of the MagnaFlow system is its price-to-performance ratio. It often undercuts premium competitors while delivering similar power gains. The sound is loud enough to enjoy but not overwhelming, making it a solid all-rounder for weekend canyon runs and daily commutes.

3. HKS Hi-Power Exhaust System (Cat-Back)

For owners who prioritize weight savings and JDM pedigree, the HKS Hi-Power exhaust is a classic choice. HKS has been tuning 6G72 engines for decades, and the Hi-Power system reflects that race-bred experience. It uses a unique, large-diameter baffled muffler that is significantly lighter than its stainless steel counterparts, thanks to its aluminum heat shield and slim profile. The system is designed to maximize flow with minimal weight, which is critical for chassis balance and rotational unsprung weight savings if combined with a lightweight exhaust tip.

  • Construction: Main piping is 304 stainless steel; muffler uses a combination of steel and aluminum components to reduce weight by approximately 30% compared to similar systems.
  • Design: Straight path with a large resonator and specially tuned muffler to produce a distinctive deep tone that HKS is known for. The sound is louder and more raw than the Borla or MagnaFlow.
  • Installation: Direct fit, but may require slight trimming of the exhaust hangers for perfect alignment. All hardware is included.
  • Performance: Ideal for high-horsepower builds; the open flow supports up to 600+ wheel horsepower without becoming a restriction. Gains of 15-20 HP are common on mildly modified engines.
  • Warranty: Limited one-year warranty; HKS expects the system to be used in performance applications.

The HKS Hi-Power is best suited for the enthusiast who plans to push the 6G72 beyond 400 whp. Its aggressive sound and lightweight construction make it a favorite on track days, but the increased noise level may not be ideal for all daily drivers.

4. Greddy Revolution RS Exhaust System (Cat-Back)

Greddy's Revolution RS system offers a modern twist on the traditional cat-back. It features a polished stainless steel finish with a large, angled muffler that provides a distinct aesthetic. The RS series is engineered to produce a deep, aggressive note without excessive drone, using a specialized internal structure that cancels out resonant frequencies. For the 6G72 twin-turbo, this system is often praised for its ability to manage sound while flowing exceptionally well.

  • Construction: Full T-304 stainless steel with polished tip and muffler can. The piping is mandrel-bent and smooth on the inside.
  • Design: Greddy uses a "Revolution" internal muffler design that incorporates a combination of absorption and reflection to tailor the sound. The tip is a large 120mm polished style.
  • Installation: True bolt-on with no modifications required. Comes with all necessary gaskets and hardware.
  • Performance: Similar to the MagnaFlow in flow rates, but some users report slightly better spool characteristics due to the resonator design. Power gains are typically in the 12-18 HP range.
  • Warranty: Limited lifetime warranty on manufacturing defects.

The Greddy Revolution RS is an excellent middle-ground option for those who want a flashy, polished look with a refined yet sporty sound. It pairs well with other Greddy intake and intercooler components if you plan a staged build.

5. APEXi N1 Exhaust System (Cat-Back)

The APEXi N1 is perhaps the most iconic exhaust system for Japanese sports cars of the 1990s and 2000s. Its signature single large tip and droning, deep note have made it a staple in the 6G72 community. The N1 uses a straight-through glass-packed muffler design that prioritizes flow above all else. This is a loud system, but its performance credentials are undeniable, especially for turbocharged applications where minimal back pressure is critical.

  • Construction: Stainless steel piping with a durable, powder-coated or polished tip (depending on variant). The muffler can is typically left raw stainless or coated.
  • Design: Straight-through perforated core with high-temperature fiberglass packing. The large single tip exits at an angle to match the bumper cutout.
  • Installation: Std bolt-on using factory hanger locations. May require slight adjustment of the tip for centering.
  • Performance: Excellent flow characteristics; recommended for high-boost applications. Power gains are among the highest of the group, often reaching 18-22 HP on a stock turbo system. The reduced restriction helps lower EGTs by 30-40°F under load.
  • Warranty: Limited manufacturer's warranty; packing may need replacement after 2-3 years of heavy use.

The APEXi N1 is the go-to for aggression and maximum flow. If you track your car or regularly attend meets and want the loudest, most distinctive sound, this is your pick. However, be prepared for significant drone on the highway, especially when the muffler packing begins to wear.

Key Considerations When Choosing an Exhaust for the 6G72 Twin Turbo

While all five systems above perform well, your choice should factor in several specifics related to the 6G72 platform. First, decide between a cat-back system (retains stock downpipes and catalytic converters) and a turbo-back system (replaces everything from the turbo outlet to the tailpipe). Most of the systems listed are cat-back, which is a great start. However, if you are already planning to upgrade your downpipes and high-flow cats or test pipes, ensure the cat-back component matches the diameter and flange layout. Many owners pair a 2.5-inch or 3-inch downpipe setup with a 2.5-inch cat-back for a well-matched system. Also note that 1991-1993 and 1994-1999 6G72 twin-turbo vehicles have different body styles and exhaust routing—check compatibility with your specific chassis.

Sound vs. Performance Trade-off

Loud systems (APEXi N1 and HKS Hi-Power) generally flow better because they use minimal sound deadening. But they can induce fatigue on long drives and attract unwanted attention. Systems like Borla and MagnaFlow offer a better balance for daily use without sacrificing much power. If you plan to use an ECU tune, the exhaust's ability to reduce back pressure directly correlates with how safely you can increase boost and timing. A freer-flowing system allows your tuner to extract more power without exceeding safe EGT thresholds.

Material and Longevity

All systems here use stainless steel, but grades differ. T-304 (Borla, Greddy, MagnaFlow) offers maximum corrosion resistance and a bright polish. The HKS uses a mix, and the APEXi uses standard stainless; both may show some surface rust over time, especially in salt-belt states. If you live in a snowy region, invest in a system with T-304 for peace of mind. Additionally, consider whether the exhaust uses slip-fit connections or flanged sections. Flanged systems (like Borla and Greddy) are easier to remove for maintenance and less prone to leaks.

Installation Tips for 6G72 Twin Turbo Exhausts

Replacing a cat-back exhaust on a 6G72 twin-turbo is generally a weekend DIY job, but a few tricks can save headaches. First, soak all exhaust hanger bolts and flange nuts with penetrating oil a day before. The OEM studs can be brittle. Second, have replacement gaskets on hand, especially for the flange connecting the catalytic converter to the cat-back. Even if the system includes gaskets, the factory gasket may disintegrate during removal. Third, use a jack or stand to support the system during installation to avoid stressing the hangers. Finally, after initial installation, run the engine, check for leaks, and tighten all clamps once the system has heat-cycled. A re-tighten after a week ensures long-term sealing.

Maintenance and Longevity of Performance Exhausts

Performance exhausts require minimal upkeep, but a few practices extend their life. If the system uses packing (MagnaFlow, APEXi N1), the internal material will eventually burn out, making the exhaust louder and potentially developing a raspy tone. Re-packing is possible for some mufflers but often not user-friendly; expect to replace the muffler or whole system after several years of hard driving. For stainless systems, occasional polishing with a stainless cleaner keeps the tips looking new. Inspect hangers and welds annually for cracks, especially near the muffler mounts where vibration is highest. Avoid using anti-seize on stainless bolts to prevent galvanic corrosion; instead, use a copper-based antiseize if necessary.

Conclusion

Choosing the right exhaust for your 6G72 twin-turbo comes down to your performance goals, daily driving tolerance, and budget. The Borla 140086 offers premium quality and sound for a sophisticated daily driver. The MagnaFlow 16580 delivers excellent flow and a great sound at a competitive price. The HKS Hi-Power is the lightweight champion for track-focused builds. The Greddy Revolution RS balances style and refined acoustics. And the APEXi N1 is the ultimate flow monster for those who prioritize maximum power over cabin comfort.

Whichever system you choose, pair it with a proper dyno tune to fully realize the gains. The 6G72 responds wonderfully to reduced back pressure, and a well-chosen exhaust not only boosts power but also improves the reliability of your turbos by lowering heat and stress. For further reading, check out resources on 3Si (3000GT/Stealth International) forums for real-world user reviews and installation guides, and consult RS Warner for high-flow downpipe options. Happy boosting!