Ok, I have completely gone through the carbs, everything is clean and unobstructed. Even installed new diaphragms. Sync is about as close as I can get it using a carbtune. New plugs even. Yet at idle I am still getting an occassional popping or chuffing (whatever) and if hit hard from idle, it doesn't rev immediately; sort of wants to stammer then rev. What am I missing here? Any advise would be most helpful.