Genuine VW/Audi Engine Air Intake Vacuum Check Valve - N90794401 - Genuine VW/Audi Engine Air Intake Vacuum Check Valve - N90794401 is a replacement for the OEM part that helps to maintain the correct air/fuel mixture in the engine. It is designed to prevent the engine from stalling or running too rich when the throttle is closed. The valve is made of durable plastic and is designed to last for the life of the vehicle.