Except 5.2L 4-Bbl.

As the throttle blade opens, a slotted port in the carburetor base or throttle body is exposed to an increasing percentage of manifold vacuum. This port is connected through an external nipple to an EGR solenoid and/or transducer and then to the EGR valve. The flow rate is dependent on manifold vacuum, throttle position and exhaust gas backpressure.