Originally Posted by Reatki
Tips don't change the sound.
Yes they do, the sound echos in the larger tips.
I wouldn't have believed it myself but years ago my brother put exhaust on his truck but didn't have money for tips at that time. Rode for a few weeks then went and had tips installed and it changed the sound a good bit.
Personally I'd go with a 4" tip. It won't make it louder but it will echo more making a deeper tone.