I have a 2008 LTr 450 with the following mods done to motor..Yoshimura did the headwork(porting polishing etc)Yoshimura Exaust, Power Commander, Yoshimura Cams. The machine has been great until I installed the cams. The valves seem to come out of adjustment about every few hours of riding. I am also running a fuel atv air filter. The shop that I bring it to has been in contact with Yoshimura and no one seems to able to find an answer to the problem. The heads have stock springs, but Yoshimura says that should be just fine. Has any one ran this set up.....I am at the point where I pretty much pist at the machine and everthing else that has anything to do with that machine.:swoon2: It is not fun getting your quad out of the shop and knowing it will break within a matter of hours..