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aloha,

on my bus, there is a rigid plastic hose which connects the power brake servo to the intake plenum. your bus has dual carbs(?), mine is FI, so i am not sure about your setup, but if you have power brakes, there must be this line to power the servo. the servo vac line has a non-return valve which can go bad, as well as a few rubber seals. if any/all go bad, you can get the behaviour you describe.

scott lyons

to anyone that enjoys forces @ equilibrium, pandoras box, etc.: while driving VW '76 Bus T4; I step on brake and engine either idles higher, the same, or lower, on a whim. But it is the same thruout ride. I must take out of gear and brake and maintain gas before it stalls sometimes. Any help much appreciated. Aloha and Mahalos from Oahu.

sounds like a vacuum leak in the line, gonna have to check the line from the front to the rear