V8 Engines
On V8 diesel engines, vacuum from the vacuum pump is modulated by the vacuum regulator valve (VRV) mounted on the injection pump. Vacuum is highest at idle and decreases to zero at wide open throttle. The EGR valve is therefore fully open at idle and closed at wide open throttle.
A response vacuum reducer (RVR) is used between the VRV and EGR valves to allow EGR valve to change position quickly as throttle position is changed. A solenoid in the system shuts off vacuum to the EGR valve when the torque converter clutch (TCC) is engaged.