Vacuum Modulator & Valve
WARNING: This page does not describe the selected car, but rather 124 other vehicles, including the 1991 Chevrolet Pickup, 1991 Chevrolet Cab & Chassis, 1988 GMC Vandura Special, 1988 GMC Vandura, and 1988 GMC Value Van. However, it is still accessible from the selected car via links, so may be relevant.
Install modulator valve into case with stem end out. Install new "O" ring seal on vacuum modulator. Install modulator into case with vacuum hose pipe facing front and angled 5 degrees toward top of case. Install modulator retainer with curved side of tangs inboard. Tighten attaching bolt.