My 91 Vanagon Multivan has a rebuilt 2.1 motor by Boston Bob.

It has 5k on the new rebuilt motor.  117k on vehicle

It has a rough idle, hiccoughs during acceleration and at cruise
speed.....actually at all speeds.

Shop has done a pin test....all ok.   Has the new wiring patch.  New good, plug
wires, plugs, new distrributor, new alternator.  Idle stablizer cleaned and
working.

ECU checks out ok, swapped with another 91 and had no change.  Ground wires have
been checked.

C o 2 has been set, timing good, all tune up done to specs,

No mechanic seems able to get to the bottom of the problem.

Power down I estimate 20 % from old motor.  Using good 91 octane fuel.  Oil chg
every 3 k, castrol 20-50.  4 speed trans.

Any ideas?

John Russell in Austin.