My wife's '93 Ramcharger had problems just like yours nearly every year. Every time it was the cheap muffler shop cat was shot. The last one we had installed was at a real shop with the correct Walker cat con. It was about twice the size of the cheapy univeral muffler shop junk. Once, several years ago, we thought it was the EGR, replaced it, we were wrong, only last year did it really need replaced.

Robert