Pontiac Repair: 2000 Pontiac GP GTP Lean Condition, pontiac grand prix, vacuum leak

Question
Hi Todd. I have a recurring problem with a 2000 Pontiac Grand Prix GTP with 109k miles.  Get codes P0131 and P0137, low oxygen sensor reading for both sensors.  Both sensors replaced. Heater circuit seems fine.  Initial problem occurred during hard acceleration.  Boost was erratic and low (as noted on dash indicator). Checked fuel pressure. Slightly low (40 psi at idle).  Replaced fuel filter. Ran car hard several times, better, full boost and smooth, no code for two days. Then it came back again on hard acceleration. Near full boost but erratic during beginning of acceleration.  Car runs perfectly for normal driving, and code will not log unless the car is pushed.  I saw a note from you about a 2-speed pump on the GTP's.  Has me curious. Ideas?

Answer
Hi Mark:
Look for a vacuum leak on this engine . there is a vacuum hose that attaches to the front of the inatke manifold right under the super charger nose piece if not there then the gasket between the super charger and the intake manifold have a tendency to leak around the same area at the hose. use some carb cleaner with the engine running and spray around that area if the rpm's pick up or the engine stubles you found the leak. Also around the injectors the o-rings that seal them to the inatke leak as well. Good luck :)