2000 Pontiac Grand Prix Supercharger not fully boosting.

The Supercharger in my Pontiac is only partially boosting. It only has 107000 miles on it, it was working just fine and then the mass flow sensor went bad so I replaced that and it still isn't boosting. Hooked it up not friend diagnostic and said purge and Pvc valve bad replaced, and still not working. Has anyone had this problem and if so what did u do to fix. Please help just want to fix my car and get back to running right.