1992 Toyota Corolla Not firing on all cylinders

My car isnt firing on all cylinders. One plug is still wet when I pull it from the engine. I switched two of the plugs around (the wet one with a dry one) and found that the problem is not the plug. The only thing that confuses me is that the plug wires and distributor cap and rotor are all brand new and look perfectly fine. What could be the problem?