well even if they are not " qualified " mechanics, if they know more about cars and vehicles then you id probly take their advice. ( where did you take it if you dont mind me asking, auto zone or something ?) anyways, like i said, a cracked or rusted or broken muffler is a pretty easy problem to diagnose, just by the idling and engine sounds as you stated. basically the importance of getting it fixed is just how long you want to deal with the problem, think about it, hear it etc. if its really bad and leaking fumes anywhere in your cabin i would get a new oem muffler . so basically the consequences are just how long you want to deal , hear, and drive with a cracked or rusted out muffler. remember, it will only get worse, rust, crack what ever. and of course the worst consequence is that you wait to long, think its all good and will be fine, then your muffler finally comes of driving 75 mph down the highway and becomes a deadly projectile that could seriously injure you , your passengers, and anyone else who may be driving behind you / on the highway in general. iv e seen a muffler fly off in a 45 mph zone a few years ago when i was following an older vehicle that was spurring exhaust fumes, and a busted off muffler can be a very dangerous thing , i was honestly scared when i saw that rusted piece of metal fly right over my driver side mirror. long story short, id just get it fixed, it will be worth the money in the end and the piece of mind that your muffler isn't going to fly off at some unexpected moment. just my 2 cents. good luck buddy. never underestimate the pros of keeping your car running properly, no matter how old, junky etc. cheers friends !
