Help me diagnose, please.
 

I did some searching but couldnt find any threads with the symptoms my 1990 miata is having.

Set up: Greddy turbo, intercooled, 1.8 injectors, Vortech 12:1, Toyota cops.

Issues: A few months ago i had a ignition problem. My car would idle but only ran on 4 cylinders in WOT. So I changed over the COPs and that took care of that. Iv put about 200 miles into now and the same problem is happening again except its not as harsh.

Breakdown: At a cold start up, when im lucky she (my miata) will start and idle like normal. 15 minutes of driving (when reached to normal running temp) she starts to stumble during low throttle like its running on 3 cylinders. Its not consistent but enough to be annoyed. Once Im in WOT the 4th cylinder comes back. After about 30 minutes of driving the idle will then start jumping up and down between 1500 and as low as shutting down sometimes. When i shut her off and try to start back up (takes a minute) She'll be shooting fuel straight out the exhaust while running on 3 cylinders again. I rev up to about 3-4 rpm and it clears up. And that will repeat over and over.

Im running 7e plugs at 40 gap. Iv swapped the AFM and still experience the same thing. Any ideas?