Engine Oil from thermactor plug?

Does this make any sense to you guys... I have oil (at least looks and feels like oil) leaking out of thermactor plug on the front of the left (driver) side head. I assumed I had a bad exhaust valve seal but I just checked and none of the plugs have any signs of oil getting in a cylinder. Where else would oil come from to leak out of the thermactor plug? Heads are AFR 165's.

Thanks. I took the plug out. It was wet and oily but could be unburnt fuel mixing with the exhaust carbons. Interestingly, the motor seems like it's running very rich (at idle anyway), but I have an Edelbrock Pro Flo 4 system on it and the ECU says the O2 sensor is seeing 13.9 which, while slightly rich, doesn't seem like it should be burning my eyes.

That's a different problem to sort out but for now, what is recommended for sealant on the plugs? I used anti-sieze since it's a steel plug going into the aluminum head. If that's not good, please advise what should be used. When I put the heads on originally, I used regular thread sealant like you'd use where a bolt goes into a water jacket.