Hi everyone; I'm restoring a '70 1800E with the B20E engine that continues to experience a high idle (~1700-2000rpm) regardless of adjustments I'm making to the throttle stop, idle screw and/or timing. What I mean here is that I can get the idle higher via these adjustments, but can't bring it down to spec. I've been engaged in a lot of troubleshooting and I think I've traced the problem back to a leaking brake Servo that is allowing additional (unwanted) air into the intake manifold. At idle with the throttle plate seating well I blocked off all other air intakes, including the vacuum line from the Servo cylinder, which resulted in a sweet sounding purr at about 900rpm. When I open the Servo line again the idle jumps up to the unwanted ~2k and stays there...hence my conclusion of some type of Servo leak.

Has anyone had similar symptoms, conditions, or experiences? The Service Manual says there is no repair available for the Servo so I'm contemplating my next move...any suggestions? Thanks