1991 Nissan Pathfinder 1991 Pathfinder misfiering, sputteri

The truck runs rich, upon giving gas the rpms are low and the trucks spits and sputters. The truck has new plugs, wires, distributor cap fuel filter and air filter, the EGR valve was also just recently cleaned out. The truck is straight piped, no catalytic converter. The only thing I have noticed wrong is the spark plug threads on one of the cylinders is stripped so the spark plug keeps spinning. I am lost and don't know what it could be and have no money to put it in the shop. What could be wrong with it? There is no Check Engine light on and I have had it hooked up to the computer and there is no stored codes in the computer.