Subaru WRX and STi Exhaust general info:
I have an 08/09 WRX, is the downpipe the same? No. The 08/09 WRX has a unique exhaust in that it’s downpipe is the same, fitment wise, as the Legacy GT. So if you have one of these models, you must ensure you state your model/year to your vendor or specifically request the “Legacy GT downpipe” for your car in order to assure proper fitment.
I have an 08/09 WRX/STI, is the exhaust the same as the 02-07 models? No. The 08/09 WRX has a unique exhaust in that it’s axle back portion is mounted differently. So if you have one of these models, you must ensure you state your model/year to your vendor or specifically request the “08/09 exhaust” for your car in order to assure proper fitment. Yes, the picture above isn’t a perfect representation of your car but it gives you an idea of where to pieces are located.
Can I use an OEM STi exhaust on my WRX? Yes, but do not use it thinking you now have an upgraded exhaust. While the piping is slightly larger in diameter, the catalytic converter is larger and more restrictive so any gains are negated. About the only reason to swap out components is to go to the STi axleback muffler which is slightly louder than the OEM WRX unit.
How do I stop my car from sounding like a “Honda Killer Bee Exhaust”? Subaru boxer configured engines, even equipped with a “Honda Killer Bee Exhaust” will NOT sound like a buzzy, annoying exhaust due to the motor’s natural sound. The only way to become buzzy is to switch to an equal length header. The OEM exhaust manifold and aftermarket unequal length manifolds (headers) retain the exhaust pulses at different intervals which create the unique boxer sound. This is why your stock exhaust sounds similar to a VW Bug or Porsche engine.
Which manufacturer is best? This topic is highly debated. There have been no reported consistent “bad” exhausts on the market. Obviously, there may have been bad exhausts sold, but not enough to report as “bad” overall.
What exhaust metal material is best? Exhausts are made from mild steel, stainless steel (304 & 321), and titanium. There is no irrefutable evidence that one material is better than the other. Obviously, corrosion levels are higher with mild steel (coated or otherwise). Article on exhaust materials.
Which exhaust diameter is best? Exhausts have 3 diameters:
1. 2.5″: Good for 300-350 HP
2. 3.0″: Good for 500-600 HP
3. 3.5″: Good for 600HP +