I don't think those are meant to be serviced by anyone. Does the vacuum line from the booster to the manifold have a hole/crack in it. Sometimes those things go bad. I have never seen a booster go bad.
The hose is good, the leak sounds like its coming from behind the booster. when I plug the hose the sound goes. I havent tired to spray any engine start around the area with the engine running to see if the idle increases yet.