95 V-6 Missing

I had some emission problems, changed the 2 O2 sensors before the converter, Mass Air Flow, EGR, put on a performance cat, and flowmaster, but now have a miss in the engine. Worse when it is cold, but still does it alot when hot. Strange thing is, it will quit every once in a while and even the service engine light will go out. All the OBDII tells me is multiple engine misfires....well DUH! I could have told it that myself. I had changed the plugs, wires, cap and rotor not long before I had the emission problems....any ideas?