'91 200q 20v stalls after acceleration & then clutch

[Gideon Weisz <gweisz@nilenet.com>]

hi
i wonder if anyone else has experienced the following.
sometimes (often), if i accelerate rapidly
and then disengage the clutch (and leave it disengaged)
the engine stalls.
1) this has not been repaired by swapping idle control units
2) i should also note that even when the engine doesn't stall,
   it fairly often goes down to 250 or 500 rpm, according to the tach,
   under the conditions i mentioned. my understanding is that that
   isn't normal behavior either.
does this ring any bells?
thanks,
gideon
(gideon weisz,
boulder, co)