Wow, I just got my 03 yz450 cam installed in my 99wr400. All I can say is WOW. Starts first or second stab, no starting drill. The added power the yz cam gave me is great as well. I really didn't notice a difference down low, but I had the stealth fuel screw and gytr insert installed as well, so maybe that made the difference there. I'm gonna drop the front sprocket a tooth (once I get ahold of my buddies electric impact), then the next project is an EFM auto clutch. I have to say the yz cam is probably the best mod I've ever made on any bike I've owned. Thankns to my buddie from our offroad group (MAX) for doing most of the work. The wife just gave birth to our newest 'lil offroader Thursday. I'm stoked to get riding once things get settled at home. To anyone considering this mod, I'd say go for it!!!!