My '99 Grand Prix has the supercharger and has two serpentine belts. The one that runs the supercharger and air conditioner has a idler pulley, which broke off and fell to the ground, while riding one day. The car ran fine, just no air and no supercharger. The tensioner pulley was still in place but the belt wouldn't stay on.
The Fix: I just bought a shorter serpintine belt. It's been fine since.