I had a 2.5" lukey on my vt 97 auto and it was more than enough soundwise, middle muffler then straight through.. have heard a 3" also and there pretty damn loud with the same setup. not sure bout performance on either tho
3" dont bother it'll cause a bucket load of problems my zorst guy told me, any exhaust place worth their salt will advise you against it..
i just got a 2.5" on my VT and it sounds great .. its loud but not loud enough to be getting pulled over
3" will get u pulled over all the time
i have a v6 auto vt, and a 2.5 was more then enough, you dont want to go overboard. im assuming 3 inch would sound a bit like a truck on a bad day... just my thoughts