XIRFOREVER,
This is a Exhaust Gas Recovery valve, This is used to bring the engine up to operating temp quickly by taking exhaust gasses and directing them back into the intake. Once the engine is at operating temp this valve closes off and the intake is onlt supplied by the throttle body. DANNYG is correct in saying that it reduces carbon build up but it also extends the life of the engine by minimising wear during the slow heatup times of this type of engine in cold areas. As we all know that a engine at its operating temp wears less than a cold engine. The biggest killer of engines is start up and reving prior to shut down.