i just got a 91 S10 with 241K on it that had the same problem. I first noticed a baseball size hole in the muffler. THinking thats what was making the HORRENDOUS noise, I got new muffler. It was not till I was under the truck to fix it that I noticed the pipe no even connected to the cat. Nice... a stright pipe dump on a 91 2.8L S10... My ears are still bleeding! It is fixed now and sounds much better. Now all I hear is the bad throw out bearing whining! Cant complain, 241K and starts everytime!