Well, this is the first time I saw this post
Have you been able to hook up a stand-alone (mechanical) boost gauge to verify that you are putting boost out?
On supercharged models before 96, the MAP sensors sole purpose is for the boost gauge, and nothing else. So this is my thoughts on what is going on:
1) MAP is toast. Unlikely, but possible.
2) Vac/boost line going to MAP is either cracked or perhaps it somehow got a checkvalve installed, allowing vac to go through it, but no boost.
3) Boost gauge itself is defective.