When in 1st gear (not L), but 1st, the truck builds power quickly until the governed 2,300 ish rpms. Under full throttle, about the half the time it seems to cut out and smoke a little blue smoke at that rpm....sometimes it doesn't. If not WOT, it will rev smoothly and higher. In higher gears it doesn't stumble at all. Is the cutting out a simple function of the gsk, or do I have a leak or something?