Anyone understand how the Mopar S3 PCM boost control works?

[srt4evah]

Because mine is being a bitch to me. I've been fighting this for months and had it to a few shops now, paid money and got nothing done that fixed it... here's the situation:

Setup
Stage 3 w/toys
AGP S3 WGA
Needswings 3" DP with e-cutout
Upgraded fuel rail w/return line
Fuel dialed in with 1:1 RR FPR at 11.4 under WOT (cutout open)

The situation
Used to hit 25psi and drop off to 20-21 at redline consistently, cutout open or closed
Now picks a random boost level, from 18-23psi, and may hold it, or may drop to 16-18psi instantly, not smoothly, and stay there for a while even on consecutive runs (won't go back up to 20+ until later on)
Holds boost just fine with a MBC

The attempted remedies
Fixed all boost leaks, tested and retested
Replaced all vac lines, perfect now, no leaks, reset computer many times, played with WGA many times... removed vac line from turbo (actually on accident) and it spiked 29psi, so it can make the boost, just won't hold it on PCM control

So... what the hell is causing the PCM to pull away the boost? It's as if it's seeing a lean condition, which it's definitely NOT, or knock, which it is ALSO not seeing. I have a scan gauge and I see NO KNOCK when it pulls boost back to 18psi, and I have an AEM wideband and can watch the A/F ratio pegged at 10 flat with the cutout closed and it still keeps the boost away. WTF?

Could it be wiring to the solenoid that's messed up? I replaced the solenoid itself with a brand new one already. It can't be the WGA, or it wouldn't hold boost with the MBC.

It HAS to be something the PCM is doing... so what could it be???

[srt4evah]

Oh and another wierd thing, on my scan gauge the Waste Gate DC% drops to 0 when the boost falls off, so it's not the PCM opening the wastegate, it's just not making the boost for some reason under PCM control.