A friend and I tried putting one of these Audiovox cruise controls
into my '84 manual Westy this weekend. Something seems wrong. We set
it to use just the coil (no magnets, no VSS wire) for speed
regulation, but I've been unable to get the speed to stick at anything
other than ~35 mph in 3rd gear or ~50 mph in fourth. And even then
it's quite prone to drifting slower. Tapping the 'Accel' button often
gives a brief surge, but then falls off completely.

At first, we suspected low vacuum, and tried just about every
connection the vacuum line would fit. Then, from some gerry list
archive searches, we thought that maybe the engine might just not
create enough vacuum, so we built and installed a vacuum reserve tank,
but that didn't seem to improve anything either.

So now I'm stuck. Any hints or ideas on how to get the Audiovox CCS100
working well in a manual transmission Vanagon?

Thanks.
  -jrs