Are there any better materials than that loose fiberglass packing to use for lining the inside of a typical slip-on muffler, and where might I find it?
Regular fiber G, and the fiber G that dirt bikes use,will not hold up to the exhaust pulse wave let alone the heat generated of a V Twin, once the packing blows out the exhaust pulse wave has no place to dampen, thus the sound wave bounces in the chamber and actually causes an exhaust flow restriction. Another reason not to remove your packing.