1981 Other Ford Models engine runs rough

Engine Performance problem
1981 Other Ford Models 6 cyl Two Wheel Drive Automatic

I have an '81 Ford F100 with a 300 6cyl. Yesterday it started missing and otherwise running very rough at idle and driving speeds. I have recently changed the plugs and wires, distributor cap and rotor, performed oil change, etc. It was running fine after all that work. I checked the plugs and they were gapped correctly but fouled after only two weeks in operation. I am getting spark at the plug wires and I tried blocking the egr valve with no effect. Not sure where else to look, again the truck was running beautifully and started acting up while I was driving it.