Ok, So I just wanted to post my results of the Factory R & D P-38 Lighting AP cover. I have a 2005 CRF450R, I live in Colorado at an elevation of 5,280 ft. I can honestly say that i noticed a big difference in the response of the motor. The little bog I had is GONE! I did not change my jetting at all and i noticed a difference! Is it worth $100.00 (plus air/fuel screw)? for me it was.