Bugger on all counts..

I'm starting to consider going to SR20

Did you change anything electrical from last time?

You really need to see if the pulses from the mdis to the coils are keeping nice and consistant throughout the revrange. Using a CRO is the way to do that. Using the dwell reading on an auto multimeter would also work. Doing a simple swap of the mdis unit is a good idea, especially if it's a plugout/plugin setup.

Would be good to check the dwell on the coils to check that each of them are getting the same love.

After installing the Autronic CDI, I haven't had a moment of ignition problems..except for the Bosch plug I fried after only 1 hour of driving. I've never worried about gaps, and it ran fine at 18psi boost.

Hmm. For my spark plug incident, maybe that wasn't a plug....maybe that was the Autronic injector driver failing, even back then. It was on the same cylinder..Hmm

I hope it all goes well. I would suspect an MDIS problem. Be sure that you have a good earth for the coils, and a good earth for the MDIS unit.