The vacuum port on the back of the manifold..... which is very small.... has 2 options.

on some older vehicles..this vacuum actually controled the vents inside the car...via a single vacuum line. on newer vehicles it simply has a cap over it so it doesnt leak.

as for the electrial gremlins.... I would get a wiing diagram...and trace each wire. one by one. I am sure you might have some bare wire under the dash somewhere......

Good luck!!!!