Be careful with aftermarket exhaust add on. My experience in this area I put a new Magnaflow muffler and tailpipe on my old Tahoe which had a 350 in it. Although I can't say I noticed any jump in performance what I did notice was a huge increase in interior noise! At 2,000 RPM it was almost unbearable. I don't know how you can get free flowing exhaust without the noise however.