the only time ive blown a muffler was on my old mj when we were stuck at the camp in some deep snow (2wd) and since i was new to this i let dad drive . well he got mad and floored er. all of a sunnder black stuff came outta the tailpipe and it got louder turns out he revved it up soo much he blew the bottoe out of my still semi good muffler. and then next summed i landed on it on a big rock.... end of story the muffler is long gone now