Well I have a '96 DOHC in my '96 GT and well I was having a problem when accelerating under load. I could only give it 1/4 to 1/3 throttle or it would start to sputter. I have another fuel pump on before for N2O and I thought that that might have been the problem since the engine was fine throughout the whole RPM range as long as it was under minimal load. Well I had some Auto-lite Copper plugs in there with less than 8,000 mi and went to buy some replacement plugs but the only plugs I could get were platinum so I went with the single pole Bosch plugs. Well the problem seemed to go away for now. What is really weird is that the plugs looked fine and still had the correct gap. Has anyone had this happen to them before and what is up with those plugs doing that?
Copper plugs are great for performance, but are not so great in terms of life. They may "look" ok, but they were probably going bad and loosing their ability to transfer electric spark. It happens. It could also be your ignition wires weren't hooked up all the way, and when you changed the plugs, you tightened them up.
