512140 - GD WRX / STI Titanium 3" Cat-back Exhaust

512140 - WRX / STI Titanium 3" Cat-back Exhaust

Subaru WRX, WRX STI 2002 - 2007

Congratulations on your purchase of the COBB Tuning WRX / STI SS 3" Cat-back Exhaust! The following instructions will assist you through the installation process. Please read them BEFORE beginning the install to familiarize yourself with the steps and tools needed. If you feel you cannot properly perform this installation, we HIGHLY recommend you take the vehicle to a qualified and experienced automotive technician.

Table of Contents

Parts List

  • Rear Muffler Section
  • Midpipe
  • (2) Exhaust Clamp
  • Exhaust Tip

OEM Parts (as needed)

  • Rear Downpipe Donut Gasket
    • Subaru PN 44022AA123

  • Front Spring Bolts
    • Subaru PN 44059AA010

  • Front Bolt Springs
    • Subaru PN 44044AA010

Tools Needed



  • 3/8" ratchet

  • 3/8" 6" extension

  • 3/8" Socket Swivel

  • 3/8" 13mm socket

  • 3/8" 14mm socket


  • 12mm combination wrench
  • 14mm combination wrench

Stock Exhaust Removal

  1. Park your car in a flat,level area and allow it to cool down thoroughly.  Sometimes a fan can aid in this process.

  2. Go ahead and properly lift and support your vehicle at this time.

  3. Go around and lubricate your exhaust hangers with silicon lube (one on the mid pipe and three on the rear muffler) and all the exhaust bolts with a penetrating oil to allow for easy removal.

  4. Using your 14mm socket or wrench, loosen up the stock spring bolts in the front.  At this point most 02-07 WRXs have been modified, as you can see here, the previous owner took a flat flange and clamped it down on the donut with no spring bolts.  This not only won't seal properly and cause damage to the donut gasket, but it will also remove the one point the exhaust has to allow expansion and movement and can lead to cracking the exhaust, downpipe or even the turbine housing.


  5. Using two 14mm wrenches or a 14mm wrench and socket take one of the rear bolts from the midpipe and leave the other one hand tight.


  6. With the one bolt in the rear supporting the exhaust support the mid-pipe with your hand and undo the exhaust hanger.  Hanger pliers make this job infinitely easier.

  7. With the center hanger removed go ahead and pull the remaining bolt on the mid-pipe and remove it from the car.


  8. Middle section removed, we can turn our attention to the rear section.  Start by removing the rear hanger close to the differential and swaybar.


  9. Now remove the hanger towards the inside of the car (USDM Passenger).  If it doesn't come off easily you may need to remove the rear diffuser (if equipped).  Make sure to support your exhaust at this point to ensure it doesn't drop.


  10. Go on to remove the final hanger and remove the exhaust from your car unbolting the one on the left.

Rear Downpipe Gasket Replacement

  1. As in the case with our sample car, you may need to replace your rear donut gasket if it's damaged. To do so slip a screwdriver between the gasket and flange at the back and wiggle back and forth small amounts in several places a few times.  Eventually the gasket will come free.

    Wear eye protection.  Old gaskets can have all sorts of pieces come off as well as pieces of metal, graphite and carbon which can feel pretty terrible in your eye.

  2. Open up your new gasket for installation.  OEM Subaru PN 44022AA123.

  3. The new gasket should just slip in place on the downpipe.

Exhaust Install

  1. Now wash your hands (seriously) you don't want to get greasy fingerprints all over your exhaust, and the cleaner your hands are, the less cleaning you'll need to do later.

  2. Unwrap your COBB Catback Exhaust

  3. The dent in the midpipe is intentional for clearance.

  4. push the new midpipe into the middle exhaust hanger and line things up with the downpipe.  This end of the flange should be towards the downpipe.

  5. If noone ruined your downpipe flange previously, you should be able to reuse the OEM spring bolts and thread them into the downpipe and leave them loose.  If someone ruined your flange previously, you'll need to add exhaust or locking nuts on the back side to get things held in.


  6. Pre-install the rearmost left and right hangers on the muffler itself.  Leave the hanger for the part of the muffler towards the front of the car on the car side.

  7. Pre-install a clamp over the mid-pipe.

  8. Gently wiggle the muffler section over the midpipe and install the two right side (passenger's usdm) exhaust hangers.



  9. Slide the left side (Driver's USDM) hanger onto the muffler then up into hanger slot before bolting it back in place with the stock bolt.


  10. Wiggle everything around to make sure it's relaxed and sitting on all of the hangers evenly.

  11. Go ahead and check where your muffler sits and get it centered the way you want it in the opening by moving it around in the hangers.

  12. Once it's where you want it, tighten things down starting in the front.  The spring bolts naturally bottom out at a certain point so don't over tighten them with your 14mm socket.  And remember, this flange is designed to allow some movement.

  13. With that tightened, you'll want to tighten the clamp on the slip fit with your 13mm.  Make sure to rotate the clamp where you can tighten it but it won't hit the underside of the car or anything underneath.

  14. Now move back to the muffler and slip the tip along with a clamp over the end.  Position it where you want it.  Keep in mind if the end of the tip sits inside of the bumper it will be louder inside the car and may burn the bumper.

  15. With everything tightened down, wipe it down with a paper towel and brake cleaner to remove all the dust and finger prints.  If you don't clean it up now they'll burn in when you start up the car.

  16. Start the car up and make sure you don't have any exhaust leaks.

  17. If you're leak free you're all done!  If not go back and tighten things up a little more.

  18. Go out and enjoy!


Map Notes for 2002-2005 WRX

Can help to figure out what map you need

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