Introduction: Transforming Your Subaru Legacy GT With a Perrin Exhaust

Your Subaru Legacy GT is already a capable machine, but the stock exhaust system leaves performance and sound on the table. Upgrading to a Perrin exhaust system is one of the most rewarding modifications you can make. It unlocks a deeper, more aggressive exhaust note while also reducing backpressure, which can free up horsepower and torque. The Legacy GT’s turbocharged EJ engine responds especially well to improved exhaust flow. This guide delivers a thorough, step-by-step walkthrough for installing a Perrin cat-back or turbo-back exhaust system on your Legacy GT. We cover everything from tool selection to final break-in procedures, ensuring you get the best possible results without cutting corners.

Understanding the Perrin Exhaust System

What Sets Perrin Apart

Perrin Performance has a strong reputation in the Subaru community for precision-engineered, durable components. Their Legacy GT exhaust systems are typically made from T304 stainless steel, mandrel-bent for smooth flow, and feature CNC-machined flanges. The exhaust is available in a few configurations:

  • Cat-back exhaust: Replaces the piping from the catalytic converter back to the tips. A great starting point for sound improvement and mild performance gains.
  • Turbo-back exhaust: Includes a downpipe and replaces all exhaust piping from the turbocharger outlet. This provides the largest power gains and most dramatic sound change. Requires a tune to avoid boost creep and check engine lights.
  • Optional muffler or resonator choices: Perrin offers different muffler designs to tailor volume and tone. The “single exit” and “dual exit” options affect look and sound characteristics.

Before you begin, verify the exact Perrin model number for your Legacy GT (typically 2005-2009 LGT). Buying from an authorized dealer like Perrin Performance ensures you get the correct parts and hangers.

Expected Benefits

  • Deeper, sportier exhaust note without excessive drone (especially with resonated versions).
  • Reduced exhaust restriction, helping your turbo spool more quickly.
  • Minor weight savings compared to the heavy stock exhaust.
  • An aggressive aesthetic look with polished or burnt-tip options.

Tools and Materials Needed

Having the right tools and supplies will make the installation smoother and safer. Gather these items before you start:

  • Socket set (metric, 10mm, 12mm, 14mm, 17mm, 19mm typically needed)
  • Wrenches (combination or ratchet wrenches in matching sizes)
  • Torque wrench (to avoid over-tightening and warping flanges)
  • Jack and jack stands (or a lift if available)
  • Penetrating oil (like PB Blaster or Kroil) – essential for rusted hardware
  • Exhaust hanger removal tool or large flathead screwdriver and pliers
  • Safety goggles and gloves
  • Perrin exhaust system (confirm all parts are included: pipes, gaskets, bolts, hangers)
  • New gaskets if not included (suggest copper gaskets for better sealing)
  • Anti-seize compound (for flange bolts to prevent future seizing)
  • Rust penetrant spray

Preparation Steps: Safety and Workspace

A well-prepared workspace speeds up the install and prevents mistakes.

  1. Park your Legacy GT on a flat, level surface. Engage the parking brake.
  2. Chock the front wheels to prevent rolling.
  3. Raise the rear of the car with a jack and place sturdy jack stands under the rear jack points. Ensure the vehicle is stable before crawling under.
  4. Let the exhaust system cool completely if the car was recently driven. Hot components can cause severe burns and make bolts expand, making removal harder.
  5. Spray all exhaust flange bolts and hanger bolts with penetrating oil. Allow it to soak for 10-15 minutes.

Removing the Stock Exhaust

Step 1: Access the Exhaust System

With the car safely raised, lie under the rear and inspect the exhaust routing. The stock Legacy GT exhaust runs from the downpipe (turbo outlet) through the mid-pipe and mufflers.

Step 2: Disconnect the Flange Bolts

Using a socket and ratchet, remove the bolts connecting the downpipe to the mid-pipe section. For stubborn bolts, use a breaker bar or an impact wrench with care. Apply more penetrating oil and let it sit if they resist. Do not force them to the point of stripping; if a bolt spins but does not loosen, a nut on the backside may need to be held with a wrench.

Step 3: Remove the Exhaust Hangers

The exhaust is suspended by rubber hangers. To free the stock system, depress the rubber grommets or use a hanger removal tool. You can also use a flathead screwdriver to pry the hanger studs free. There are typically four to six hangers along the system.

Step 4: Drop the System

Once all bolts and hangers are detached, the stock exhaust will be free. Slide it out from under the car. It may be heavy and unwieldy; have an assistant help you maneuver it away. Set it aside for later disposal or recycling.

Installing the Perrin Exhaust

Step 1: Check New Hardware

Lay out all Perrin components and compare them to the instructions. Verify that gaskets, bolts, and hangers are present. Perrin systems typically use high-quality gaskets, but you may want to use aftermarket copper gaskets for a better seal. Apply a thin film of anti-seize to all bolt threads.

Step 2: Install From Front to Back

Begin at the downpipe connection. For turbo-back systems, start with the downpipe. Secure the downpipe to the turbo outlet flange using new gaskets and supplied hardware. Tighten bolts hand-tight first, then torque to 35-40 ft-lb (check your specific system specs).

Step 3: Connect the Mid-Pipe

Slide the mid-pipe into position and attach it to the downpipe or cat-back section. Align the flanges and insert bolts. Only snug them initially to allow adjustment.

Step 4: Hang the Muffler(s)

Place the muffler section(s) into the rubber hangers. Press firmly to seat the studs. Adjust the position of the muffler so that the tips are centered in the bumper cutouts and the system does not contact the body or suspension components. A loose system will rattle and may cause damage.

Step 5: Tighten All Connections

Once everything is aligned, tighten all flange bolts to the recommended torque using a torque wrench. Over-tightening can warp flanges and cause leaks. Check the hangers again for secure attachment.

Step 6: Final Position Check

Start the engine (with the car still on jack stands) and listen for any leaks or rattles. If you hear a hissing sound at a flange, tighten slightly or inspect the gasket. Also, check that the exhaust tips are not touching the bumper cover. Adjust by loosening bolts, repositioning, and retightening.

Final Checks and Break-In

Post-Install Inspection

  • Re-torque all bolts after a short test drive once the system has thermally cycled. Heat cycles can cause bolts to loosen slightly.
  • Check for exhaust leaks around all gaskets. A soapy water spray bottle can help identify small leaks (bubbles will appear).
  • Lower the car and perform a full road test. Listen for drone, rattles, or exhaust scraping over bumps.

Break-In Process

T304 stainless steel and new gaskets benefit from a brief break-in period. Drive moderately for the first 100-200 miles, avoid sustained high RPM, and then re-check all fasteners. This ensures the gaskets seat properly and the system settles into its final position.

Performance and Sound Expectations

A Perrin exhaust significantly alters the Legacy GT’s character. The stock exhaust is quiet and restrictive; the Perrin cats bring a deep, aggressive rumble at idle and a hard, purposeful roar under full throttle. Expect:

  • A pronounced increase in turbo spool sound, especially with a turbo-back system.
  • Estimated power gains of 10-15 whp for a cat-back and 20-30 whp for a turbo-back with a proper tune (source: Cobb Tuning forums).
  • Interior drone levels depend on muffler choice and resonator presence. Researched models are livable for daily driving.

Real-world experiences from the community, such as on NASIOC, confirm that the Perrin exhaust is one of the best-sounding systems for the Legacy GT when paired with a downpipe and tune.

Maintenance Tips

  • Cleaning: Periodically wash the exhaust tips with a quality metal polish to prevent tarnish on stainless steel. For burnt tips, use a gentle cleaner.
  • Hardware inspection: Every oil change, check flange bolts and hanger conditions. Corroded hangers can cause sagging.
  • Rust prevention: If you drive in winter or in salted road areas, consider applying a light coat of high-temp paint on welds and exposed areas to minimize corrosion.
  • Gasket replacement: If you ever need to remove the exhaust, replace the gaskets to ensure a leak-free seal.

Troubleshooting Common Issues

Exhaust Rattle

Rattles usually come from the system contacting the underbody or heat shields. Double-check clearances around the driveshaft, crossmember, and rear sway bar. Adjust hangers or use a pry bar to bend heat shields away.

Exhaust Leaks at Flanges

If a leak persists after tightening, the gasket may be damaged or the flanges may be warped. Remove the section, clean both surfaces, and install new gaskets. Apply a thin bead of high-temp RTV (if using a flat gasket style) for extra sealing.

Drone at Highway Speeds

Some drone is natural with a more open exhaust. If it is excessive, consider adding a resonator (Perrin sells separate resonated mid-pipes) or upgrading to a louder muffler option. Drone usually improves as the system breaks in and develops carbon deposits that dampen sound slightly.

Conclusion

Installing a Perrin upgraded exhaust on your Subaru Legacy GT is a satisfying weekend project that delivers a clear improvement in both auditory and driving pleasure. By following this detailed guide, you will ensure a leak-free, properly aligned installation that lasts for years. The key steps are preparation, proper torque, and careful alignment. Once completed, you will enjoy a more responsive, better-sounding Legacy GT that turns heads and puts a smile on your face every time you start the engine. Take your time, use quality tools, and appreciate the transformation.