i have a 07 yfz450 with an intake and exaust on it. The quad has great torque in the bottom end but when it gets to the top end it feels like it has very little to none. I also have bone stock 08 yfz450 and it will beat my 07 in a drag race. The gearing is also the same but for ome reason you have to shift the 07 quicker My 07 yfz that im having the problems with does bog when u give it full throttle instantly to if you hold it it will die im not sure if thats a jetting or not. i also have a motorcross track wich has a lot of sand and I could be in a 5th gear and give it full throttle and it wont bog even if i should be in 3rd gear. The guy i bought it from said the motor is stock but it has high compression and thats why i run it on race gas. So could anyone help me out thank you!