Originally Posted by mikeditka
I'm basically wondering the PRO/CON (mostly as for as performance and power) between...
1) test pipes removing the primary cat...all else stock
2) straight pipes through the muffler...all else stock
3) cheap x-pipe...all else stock
4) test pipes and x-pipe
***test pipes and Remus Race*** (still expensive, but I had a Remus on e and loved it so much)
Exhaust is normally such a simple thing, but the way they have the cats on these and the exorbitant cost of some of these brands is just unreal
I get frustrated b/c there is a million vids of "e92 straight pipes" but the EXACT setup remains a mystery. Some are truly header out the back straight pipe, some aren't...I want to believe that a truly great performance/sound combo can be had under $1,000
I'm no expert, but from what I gather on the forums, the main performance gain is from the removal of the primary cats, approx 15-20hp. The removal of the secondary cats I believe is somewhere between 5-10hp but the added increase in rasp and exhaust odor may outweigh the performance benefits for some people. HFCs may be a good option if this is a concern. As far as I know, the stock axle back exhaust is pretty efficient, so there are minimal gains to be had here, although some vendors claim a few hp here and there.
So generally speaking your choice of test pipe or xpipe configuration will determine your (exhaust related) power increase over stock, and any addition of resonators or axleback system will just vary the sound you end up with which can vary from a high pitched scream to a deep growl depending on which configuration you end up with. You can find numerous videos of many different configurations on youtube and throughout the forums. The cheapest route, just replacing the 4 cats with custom straight pipes and keeping the stock rear section will net most of the performance that there is to be gained and would only cost you a few hundred bucks at a local exhaust shop. You will end up with a somewhat raspy sound though which some love, some hate. From there, you could step up to prefabricated test pipes for a simpler installation, a full xpipe in various resonated/HFC configurations, or a even a $6k titanium akra evo setup, whatever your budget and taste may allow for. Keep doing your research, theres plenty of options out there for every budget.
My current setup is a $400 OEM mod (perforated pipe method which sounds nice and deep) and I likely will add pre-fab test pipes for another $400. If I didnt have a E93, I probably would have went with a Megan Racing Axleback (~$500) and Test Pipes which sounds pretty good from the videos I've seen.
BTW you won't be sorry for buying an M3, even in stock form its a hell of a car!