Working on my "new" '89 (have to fix that signature...).  It was
idling around 1250 rpm, pretty steady.  I pulled the idle-stab module
and looked at it under the 'scope -- generally it looked very nice
but three of the terminals had barely visible (under 40x) solder
cracks on the top side of the board, bottom side looked ok.  One of
the diodes also had just the suspicion of a crack on top side, looked
ok on bottom side.  I reflowed all the terminals and all the large
components (caps, diodes, one resistor, driver transistors).  Result
-- on closed throttle, idles down to 1250 or so, then a number of
seconds later drops down to about 850.  I don't know whether that's
strictly normal for a 2.1 or not, but it's definitely much better.

--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage," '85 GL "Poor Relation"