Need help with cut out issue, at wits end

[Tom N]

I am at my wits end with trying to figure out a cut out issue the car has above 21psi.
98 240sx w/ stock long block S15 sr20det, rewired walbro, fmic, 20g turbo w/ internal gate, enthalpy tuned ecu, z32 maf, 3in exhaust and progressive methanol injection.

Ok heres what it does. under 21psi it runs perfectly fine. Pulls to 7800 with no problems.
If i try to turn the boost up past 21 at wot it will cut out right about when it hits full boost. It will cut out then back in like twice then start pulling again.
I have tried adding additional grounds to the engine as well as a coil pack grounding plate, replaced the coil pack harness with a new one from wire specialties, tried swapping in some 350z coils, closed the gap up to .020.
tested to see that the harness is getting proper voltage to the coils, ran 12v power to the harness strait off the battery, voltage stays about 13.3-13.5 through the pull. I`m starting to think this issue is not spark related.
a/f is good. Ive tried leaning it down a bit as well as richening it up some through the alcohol injection just for something to try.

None of these thing made any difference at all. Still will cut in and out if i go above 21psi.

would love any suggestions that maybe i`m not thinking to test.