regarding DynoMax Ulta-flow mufflers, they are just a glorified glass pack, but the packing is supposed to absorb interior drone noise, so you're saying they held up? my fearhas been after a while the packing burns out, Pypes just seem too loud and not sure on flowmaster for interior noise, there's another company making mufflers with rockwool instead of fiberglass not sure on that but it should last longer