I've got an 08 WR450 with the following mods: YZ Throttle stop screw, binoculars removed, Stock exhaust with 45MM tailpipe instead of the 29MM w/baffle. I have not cut the gray wire or removed the AIS. I ride at around 2000-4000 feet. As far as jetting goes I am running a 162 main jet, and a 48 pilot. Everything else is stock. I get backfiring and sputtering at 1/4 to 1/2 throttle. It runs great at full throttle. Do I need a new needle jet, or a bigger pilot? I've tried running bigger main jets all the way up to a 170 with no luck.