When I got my bus the vacuum line to the brake servo was plugged with a bolt. Last night I hooked it to the servo port and tried it. I can't tell any difference. To make sure it wasn't leaking all the vacuum, I pulled the hose on the distributor and it still had a vacuum so the servo isn't leaking. What else should I try to see if it's working? How much difference does it make with & without the servo? Where does the air hose on the brake rod connect to? The best I can tell it runs up into the frame never to be seen again. My book says it uses atmospheric pressure as a reference so I guess it doesn't connect to anything???? Ronnie