besides an air leak on my carb boots, one of which has already been permatex-ed, what else could be causing this? it's not awful, it's not super loud and only happens once i let off the throttle. and if i pull the clutch in things go dead silent, in a good way-popping stops. i'm pretty sure it's happening on both sides. again, short uni-foam filter upgrade and shorter reverse megaphone baffles. ??? everything else is running tip top(knock on wood).