muffler has a dent in it will this cause major problems
Unless it’s dented in such a way that it pinches off the exhaust flow, no.
It might cause it to fail prematurely…I wouldn’t worry about it.
I’d say it depends on how bad the dent is.
Don’t all mufflers get dented eventually?
Leave it alone, like everyone else does.
If it’s not crushed the muffler should be OK. If it’s a 1" deep dent then it’s OK.