1996 misfire

I have a 1996 chevy c1500 2wd automatic with the vortec 305. 130,000 miles, full tune-up at 100,000. The truck was running perfectly one evening (and had been for a long time) when I stopped at the grocery store. After about 5 minutes I returned to the truck and started it up. It was then running terribly with a bad misfire, the check engine was also flashing indicating a misfire. It also had a very rich smell in the exhaust. Truck has ran like this ever since. The misfire is throughout the entire RPM range, hot or cold. EGR?
Mass air flow sensor? I realize I can scan it and get the code (which I will do), just thought you guys might know of a problem common to this truck.