nathansays... you know if i was to replace this machine it would be with the new Raptor because they are the shit I don't care what people tell you, ride one and find out for your self. I have piped my 2004 660R with the Yoshimura Full exhaust system and jetted it to recommandation and i will tell you what. This thing kicks some serious ass. The articles are right when they say it is for experienced riders. But what i don't get is that they say it wheelies to much are they dumb. There is no such thing as to much in my opinion, I can't get enough of it. Yeah the difference the pipe made was unbelievable 11HP at top end and 9HP at low end that is unreal that brings the power out put from 35HP to 46HP WOW. after about 4 hours i had it on including the jets. After that i could not get the stock tires to hookup all they wanted to was spin so purchased the maxxis razer2 tires to balance out the power to traction. and now all i do is ride wheelies, climb hills and haulass.