2007 L32 MAP sensor @^$%^%$!!!

I have a 1988 Fiero GT with a 2007 L32 swapped in and I cannot find a MAP sensor that seems to work correctly. All the parts lookups contradict each other on which one is correct. The original one had a part # I can?t even find (22043) and I have tried 19418810, 213-1631, & AS314 plus a older larger one from my 1986 GN and all of them match the BARO at ?Key On Engine Off? at 14.8 ? 14.9, but under boos the MAP will soar up to 26 psi when my boost gauge is reading 11 tops. I was told on the 3800 forums that the correct one is actually 12580698 so I installed one but now both my MAP and BARO read only 10.6 ?Key On Engine Off? but under boost the MAP now reads correctly. I checked for adjustments in HPTuners but it's a very limited amount of tables available. Does anyone have any ideas on what would be causing this, and how to get around it?