fwiw- I think I mentioned we have been having problems with Msd units- its been the connector between the distributer to the box.
Maybe a bad run of connectors- who knows.

Indications; Power drop, running rich, then missing, then just fine, then missing, then rich.
Apparently it causes some type of signal jiggle the msd box doesn't like- at all.

I thought i had mentioned you might want to check that but it may have been some other thread.

If you use an msd checker only you can miss the problem if the connection is solid when you are checking.
Check that little connecter- wiggle it a little with engine at 2000rpm.
If thats the problem, you WILL hear it and feel it.
Msd box may be warmer as well.
Whatever that flakey connection issue does to the MSD 6AL, 6 AL2, 7- It doesn't like it one bit.
fyi