I have a 1992-S-10 Blazer, 2-wheel drive, 4.3 V6, It's been running ragged, idles rough. Runs rich. Black stuff with gas smell comes out the tail pipe. Got a code 42. Relaced the control module, timing chain, map sensor, plugs & wires, egr valve, coolant temp. sensor, fuel pump. It's running somewhat better, but still getting a code 42. Any ideas why???? Also have a noise coming under the truck around the muffler area.. HELP!!

Do a websearch for the codes for your vehicle. The condition that you describe that the S-10 is running, and was before, could have helped contribute to a failure of the cat. cvtr. which I have heard can make noise and further contribute to other problems like you describe.