Bad Spark Plug??????

[USMC302]

Thanx. After 7 mustangs I have never had this problem before, and I would probably kill myself if I would put the wires on wrong for the first time. I did check a while ago just to make sure and they are all good, the thing is, it doesn't really missfire during idle or light acceleration around town, only does it start acting up when under hard acceleration. There is a very faint pop in the exhaust during idle though, but not like a missfire you know, I have seen friends mix the wires before and man alive was it obvious but this is really really faint. I think the shims idea makes perfect sense and I am going to make sure it's not a spark plug first then check the cylinders and start shimming.

I DO have another prob though, the car when cold or hot starting will not start if while turning over to start it I let the key back too early. Almost like it is flooded. I don't give it gas during starting and the BBK FPR is set to 38lbs. I have been told this could be the coil going bad, but have just put a MSD coil on yesterday and the problem persists. Even after the car has been running a while, it won't start up again unless I let it cool for a while or sit for a few minutes. ANy ideas on that?