I have to admit I don't know crap about cars. So, my car has been running a little bit sluggish and I've noticed that back at the exhaust pipe there's an awful smell that reminds me a lot of fingernail polish remover. My step-dad hasn't taken a look at it but from what I've mentioned he thinks it's the cadillac converter? Sound accurate? And if so, does it matter how expensive of a converter you buy to replace it?