1994 Nissan Pathfinder rough idle, very rich condition once

The pathfinder starts fine, idles great, and runs great when cold. Once it reaches operating temperature, it will barely idle, smells very very rich, and runs very rough under 2500 rpms. I'm having trouble pulling codes, but I'm thinking O2 sensor? I plan on checking the MAF sensor tonight, its got a cold air intake and I recently cleaned and oiled the air filter when I changed all plugs, wires, oil, filter.