Ok here is the story

I picked up a Minty 1992 XP , the guys said it would not start when I bought it. He replaced the coil and still nothing.

I get it home remove the wiring case and open up . unplug the red/black wire from the MPEM to the coil and I have spark . Run up ski on the hose all good. Find out from another forum most likely cause is the rev limited shorted out in the black box replace box with 2 different ones and still nothing. Then I try it one more time and I have spark run it up a few times all ok. Come home today to try it to make sure and again no spark. But now the weird thing is when i watch the plugs with no spark and let go of the teather with the engine spinning down it has spark? I have done all the ground wires and check every possible wire. I don't know what I am missing. Could it be a bad relay on the MPEM box?

Please help