Have an 02 400 ex with a 416 piston 11:1, ported polished head, upgraded valves, stage 2 hot cam, full Curtis spark exhaust, k&n filter with outerwears prefilter, air lid with 6 round filters. Currently have a 42 slow jet and 170 main jet, seems to run lean, crackling top end throttle, and backfire out exhaust on deceleration.