Bruce--

I can share my experience. But it does sound a little different than yours. My
bus surged at idle and dropped, but never stalled. And I never had the engine
noise you speak of as it stalls--and again. My engine did not stall. (and I
have a 4-speed manual)

In short, I had a vacuum leak where the throttle meets the throttle body, and
the 02 sensor was bad. I found and fixed the vacuum leak and still had the
surging problem.That's when I checked the 02 sensor. To check it you can
unplug the wire to it. If the engine operates normally without it connected,
then the 02 is suspect.

Another sign of a bad 02 is sooty deposit, more than "normal" in the exhaust
pipe.If the 02 is bad chances are it fouled the spark plugs as well, and they
will have to be replaced.

My engine, by the way, ran fine when it started. But after a few minutes of
warm up it started the surging.

Good Luck
Jeff
83.5 Westy