Thanks Charles [ Cr from Texas ] for the plug for our THREAD on this very subject... and is at: http://www.peachparts.com/shopforum/showthread.php?p=1872065#post1872065. Keep your discussion here and I will put up a POST referring interested readers of my THREAD to your's here!
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Alaska240D,
Just in case I believe your car's Tranny-Shifter Vacuum Control System's diagram is the one at: http://www.peterschmidtransmission.com/vacuum/1977_1985/616_617_91/616_617_91.jpg

It sounds like you have a combo vacuum hand pump with gauge so you have the most important tool to troubleshoot your problem.

Charles already has you on the right track... but let me ask/suggest:
(a) How long have you had your 240D?
(b) Continue looking for leaks in the various parts of this system,
(c) Check and verify what color restricted orifices [#62 & #63 on the diagram for your car... report same but to us,
(d) IF the orifices are different in color, hold them up to the light [side-by-side] and report back as to which appears to be larger... and remember to keep track and replace them in their original positions. Someone might have drilled one of these out compounding your effort to achieve the proper starting vacuum. Your's appears high.
(e) Most important at this stage of troubleshooting is to put double emphasis on (b) above. You can use golf tees or other means to isolate sections of the vacuum system's plumbing lines and test for leaks.
(f) Yes, seriously consider abandoning the EGR system that branches off the Tranny-shifter system. Again a golf tee is all you need!
Regards,