Andy usually a hesitation or stumble is a lean problem. Especially since yours goes away at 3000rpm launch. First thing I'd try is turning the idle screw out a 1/2 turn or so, if its still there try a bigger squirter. Take carb cleaner and spray your air bleeds, they have little holes and tend to get plugged easily. The dye in racing fuel will gum them up also. Let me know what you find.