Valid point, I stand corrected.

 

I'm not sure where exactly they located it in the G, but it should be anywhere between a vacuum source(intake manifold) and the brake booster. Usually it's a small cylinder barely larger than the line to the brake booster itself and is attached somewhere in-line witht he brake booster line. To check it, you can simply add pressure from the intake manifold side and see if it holds. It should only allow air to go through it from the booster side.