(71 bus, stock 1600DP engine, standard carb/air cleaner)

Thanks to everyone who has provided suggestions to this pesky
problem(engine conks when foot goes off gas. Sometimes. Almost always
after engine has been revving for a minute or so, like hitting offramp,
or cruising street at 3,000 rpm. But not always. When it does, it conks
quickly, no hesitation. When it doesn't, tach shows that it slows to 950
rpm. Braking not required for conk. Engine can be hot or cold. It's an
either-or situation: either it conks or it does not. No in-between
low-idle situation where it it trying to make up its mind.).

So far I've been able to eliminate:

1. fuel pressure or delivery to bowl (engine runs fine at WOT for as
long as I like),

2. ignition (timing light mounted in rear window shows I have spark,
even as engine is stalling out)

3. brake boost vacuum leak (no problem when braking, I was wrong earlier)

as possible causes for this odd behavior

This suggests that it isn't mixture (no black smoke, no smell of
unburned fuel, and, as I mentioned, it's either-or), nor a vacuum leak
(either-or, engine hot or cold).

Prevention/Recovery Technique.

I have evolved this method of dealing with the problem: While driving I
can stop it from happening by keeping an eye on the tach when foot goes
off gas. If I am not in a panic stop situation, I have enough time to
see if the needle is dropping slowly or more quickly. If it is going
down to a stall condition, pumping the rpm's up a few times fixes it.
Pump, watch tach, pump, watch tach. The first couple pumps usually don't
do the job. The third or fourth does. Can tell right away by how quickly
the tach is falling whether the engine is in a nosedive or not.

If it does stall, the engine starts up right away with application of
starter and a touch on the accelerator.

The problem occurs more frequently and is harder to recover from when
the nose of the bus is downhill.

Unless my "Prevention/Recovery Technique" suggests otherwise, I'm
thinking I'm dealing with an idle circuit problem.

Jan proposed that when it conks I take this newish aircooled.net 34
PICT-3 Pierburg carb apart and inspect the bowl to see how much fuel is
in it. See if there is some idle circuit problem, or a fuel delivery
problem. It's the really right idea, but I don't see myself pulling over
to the side of the road and waiting for the engine to cool enough to
pull, disassemble, inspect, re-assemble and re-install the carb while I
am going about my daily stupid errands and stuff. Heck, I am not 100%
certain that I can get the carb out without pulling the engine.

I bet there are plenty of Real Men here on RAMVA that would undertake
such a task without hesitation. I am, however, a mere squirrel. Timid.

I might just get another carb and install it to see if the problem goes
away. Direct, and simple. Can sell the unused one on eBay. I would take
a loss, yeah, but I would narrow down the problem. Other than the fact
that no Real Man would use this method, is there anything I should
consider or try before going this route?