Darn vacuum line fittings! Finally found some time and pulled the entire vacuum line going around the SC and well well, BOTH fittings for each MAF were cracked.
No wonder the boost gauge was all funny like. So I used some fittings I had from Autozone and had to use the fuel regulator fitting for the rear MAF and an itty bitty replacement up front, but it all works great.
Now when I romp on it the boost gauge hits about 8.5psi (I'm guessing by GM'* very inaccurate gauge) and at high rpms she shoots WAY past 10psi...maybe 11.5. Before the gauge barely hit 10psi on a good day.
Check engine light came on, maybe because the battery was still plugged in when I disconnected the first fitting, then removed the negative terminal once I decided to dig deeper. I dunno, I don't have scantool on hand. So I'll drive on it and see if the light goes away in a day or two.