The engine vacuum pump is on the front of the engine below the big fuel filter. There are two fittings on the pump; the big one goes to the brake booster, the small one splits to serve a number of systems. Two branches go to the (US LHD) passenger side of the engine bay; one for EGR, one for the turbo wastegate. It doesn't matter which one you redirect to the turbo wastegate.

In this picture, the two fittings to the passenger side have yellow caps. This is not a 92 300SD so it might not be an exact representation.



Sixto
87 300D