Error codes 172 & 176 (both banks lean)

[Limitwheel]

My '95 ATX SHO has been throwing 172 & 176 codes. (Banks 1 and 2 lean) The MAF elements are clean. The EGR valve seems to work ok when I put vacuun to it. I replaced both O2 sensors and EGR sensor. Air temp sensor is ok. The throttle position sensor checks ok. An ideas, I at my wits end. Thanks

 

[Rob94]

Vacuum leak is letting unmetered air in. Listen for a tell-tale whistling sound, or try a spray bottle of water and mist all around the intake.

 

[SHOZ123]

If it is happening to both banks then I would suspect something before the rear of the TB.

 

[rangerj]

Check your snorkle tube for cracks or splits.

 

[sdpatt]

Another vacuum leak that can be hard to find may exist in the canister purge line that attaches to the top of the throttle body and routes down past the coil pack to the CANP solenoid valve. If you have had the intake off recently I would suspect the intake to head interface. Also, if the intake had been handled off the engine, the runner to plenum connectors can dry out and become very brittle.