I had a flowmaster. I got a 3" exhaust and that was a problem.
Should stick to 2.5" (any larger and you lose back pressure).
The sound was ominous (I set off numerous car alarms when in downtown Philadelphia) but also misleading- it sounds like a V8 but performs like a V4 <img src="/forums/images/graemlins/ignore.gif" alt="" />

Keep the same pipe diameter as stock. Might be able to get away with 2.5" but don't waste money on 3".

Currently, I am running the TRD exhaust package and its been fine. <img src="/forums/images/graemlins/cheers.gif" alt="" />