Well thanks to all who replied to my original msg with hints and tips.  Joel
sent me a note pointing me to a section in the Bentley that I had overlooked
(it's in the index up front).

I had suspected something in the vacuum area and sure enough, I discovered
that the cruise control servo unit (the one with the rubber cone shaped
bellows that pulls on the throttle) has a wee little hole in the rubber
part.  I disconnected the vacuum hose at the juction near the vacuum pump
and found that if I sucked on the tube, the servo moved but wouldn't hold
the vacuum.  I then sprayed the rubber part of the servo with windex to get
it wet and then blew on the vacuum hose and looked at the bulging rubber
cone.  There's where the tiny whole was.

Well, it did its job for some 15 years, it doesn't owe me anything, I guess.
  I looked on the Bus Depot web catalog and couldn't find one there.  I've
sent them an email inquiring about it.  So I will eventually get a
replacement, should be a simple fix

John Graham
88 Westy
Charlotte, NC

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