i have a upr o/r x-pipe and dynomax muffs, its kinda tinny but tolerable. is it true that mufflers with packing stop that? i had read that in another thread but don't know the validity of it. i have a 5.0 (4th 5.0) and i know h-pipes do the job. what mufflers do a 5.0 with an x justice?