Easiest thing to do is to plug the hose to the brake booster and see what it does.
A common check for vacuum leaks is to spray a flammable material onto the area of the suspected leak, and see if the engine surges due to the entrance of fuel into the intake. You can use something like starting fluid or propane because they dissipate quickly, but still be careful doing this- use safety glasses, have a fire extinguisher, do it in an open, well ventilated area. Spray it around possible sources of leaks, like the intake manifold gaskets without letting the fuel get into the carburetor air intake.
Topic: Non-diesel related but still a vw issue. (Read 4851 times)
