Quote: 'what does 4" exhaust do for you?'
Theresa,
Two come to mind, lower EGTs (muffler has less back pressure than stock) and faster spool-up of turbo.
Yes, in most cases, the aftermarket exhaust will be louder than stock (in my 24v, no noticeable db difference). BUT, it sure sounds great.
Lots of good systems out there... recommend getting a system that has hangers welded to exhaust pipe/muffler rather than welded to clamps.
By the way, I bought a DPP 4" 409 stainless, w/ 304 stainless tip, for $490.
Dwayne