[richtazz]

I would bet it's a vacuum leak. AT the throttle body, there is a vacuum block with 3 lines coming off. One goes to the Map sensor/PCV valve, one goes to the charcoal canister, and the other goes to the HVAC unit and cruise control servo. Follow the line for the HVAC and check for cracks (it's a hard plastic line) or a burned spot(it may have fallen against the rear exhaust manifold). The Control unit uses vacuum to switch from vent to defrost to floor, etc... and defaults to floor/defrost blend when it receives no vacuum.