That sounded dayum sweet!

 

x-pipe improves flow and will actually increase your low-midrange trq. H-pipe will do the same but is more for higher RPM's but it'll also sound louder.

I found this out on both my Mach1 and Cobra....it works very well.

If you want mean soundAND performance get high flow cats, x-pipe (not as loud as H-pipe but louder than stock) headers,and a high flow airfilter. K&N, JLT, whatever is out there for Audi's. Make sure you find someone to tune it though because this will affect your AF ratio. You don't want to detonate one of these motors- it could cost a bit to replace. LOL

Not sure how it is with Audi's but with my Mustangs I got a 40-90 whp bump.
275 to 322 RHWP on the Mach and 380 to 475 on the Cobra.

 

Flowmasters are junk for AUDI's..I took out my xpipe and noticed better torque, lower oil temperature and a meaner sound with no drone or whine. It is silent when idling which is nice because of the sleeper effect but at WOT from a standstill or on the freeway sounds F***ing good. If you are doing mufflers I highly recommend Borla or Magnaflow for a discreet sound at idle and around town but when you step on it, people will hear the ponies under the hood. Same effect as the RS6/4. You want a flowmaster? Go buy a pickup or a American made muscle car. They are great for those applications....