1998 Mystique 2.5 P304

I have a 98 Mystique with a 2.5L auto. It seems to have one heck of a misfire to it. I've pulled the codes and one of them was the #4 cylinder misfire. I've done the plugs and wires and also the upper intake gaskets. But it doesn't seem to help. The plug on the #4 cylinder keeps fouling up. I only have to run it for about a 30 minutes before the plug is completly fouled, which is probably causing the misfire. I ran the engine with the plug removed from number 4. There is only a little oil on the plug, but it almost smelled like exhaust fumes coming from the cylinder. Does anyone have any ideas as to what is going on with my car?

A couple things come to mind...

Injector harness is cracked and fuel injector is running full duty. 95-98 had problems with wiring harnesses cracking.

Coil pack is bad.

My guess is the first option.