Ignition problem again
 

I posted earlier about haveing an ignition problem with my 89 GT. Well I swapped the distributor and coil out of my 88 into the 89 and it started up.
But I still have a problem and here is what happens
I push the car full thottle up though 3rd gear(this only happens from 3 to 4 shift) up to about 6k , cause I have a cam and such, and then I let off the gas for a sec to shift to 4th, like normal. But when I hit the gas full thottle again it just cuts out like the spark is gone. Then if I release the thottle power returns and I go on my merry way.

This happened with both ignitions systems so I know now it is not that, cause the one from My 88 works fine.

Please give me a clue what might cause the ignition to turn off under high loads other then the distibutor or coil.
Thanks