Muffler blew up on 92 ranger

I have a 92 Ranger 6cyl, over 100k.5speed manual trans. The truck started to choke while driveing, like the exhaust was clogged up, so i took it to the muffler shop, had the converter,pipes and muffler replaced. the truck drove fine for about 8 miles, then started to choke again. I parked it at a friends til the next day, started it, it was still choking. I drove it a few blocks cut it off. But when i started it again, the muffler blew up. What would be causing this?