Wow..sounds like we are firing shots in the dark here.

Phat..how could you have the same problem, you have a different motor.

Dashaft.. check the vacuum lines to the SC as mentioned. I feel that you are getting some other issue as well.
Does the boost gauge return to -10 at all?

While you're checking vacuum lines, check the one that is rather hard to see and has been an occasional issue. It'* under the supercharger snout.

That line is for the two MAP sensors. One goes to the boost gauge and the other to the pcm.