How are you determining that it is faulty? The Vacuum Control Valve is designed to vent vacuum in relation to throttle position. This is done by a Y-connection to the input side of the valve.
The last time I saw a report of a suspect VCV, it resulted in the discovery of a leaking vacuum cap on the modulator.
1984 Mercedes-Benz 300SD Base Sedan - Automatic Transmission - Page 4