i have a 12v my dad has a CR and all mine has done to it is a AFE intake and straight back exhaust with no muffler and i also keep my window down just to hear my baby roar. the 12v has never let me down. the truck on the other hand.....well 224,XXX miles does some damage lol but the engine its self is unbeatable. also just put a new tranny in so it just came back to life =] lol