Bought 06 WR450F a few weeks ago. Broke it in with no problems. Had a FMF Factory 4 slip-on exhaust put on at local shop and they rejetted carb. Kept stock header. I did airbox & gray wire mod myself. AIS removal kit on back-order. Went out this past Sunday and it ran like an absolute beast for about an hour. Mostly stayed on the beach as I was with a friend who's just learning to ride. After an hour or so it started cutting out above mid-throttle. I thought I was running low on gas so i turned to reserve. Still was cutting out. I dropped into the woods for a few minutes and it ran great as long as I didn't open the throotle too wide. I'm not the smartest guy when it comes to jetting but I think this may be my problem. Anyone experience the same thing or any suggestions?? Any help would be greatly appreciated.