My 22r has started bucking like crazy under heavy acceleration and losing oil pressure at highway speeds. I pulled the (NGK) spark plugs last night and noticed white powder building up on the tips but I haven't adjusted the carb in a month & the bucking just started. The truck runs great at idle & in town but is not really highway-ready anymore. Timing is dead on, no vac leaks (tested with carb cleaner). What would cause bucking & losing oil pressure-- could it be as simple as bad gas?!