I think TourdeForce has it right. Check your coil pack as well. Should get at least 9000 ohms out of it. This sounds like misfiring. Check the plug wires closely for any minute cracks. Same for plugs as well. I has a hairline crack in one plug and it was "carbon arching". My Z-tec ran like crap until this was found. I used a magnifying glass.
Hang in there.
