To the wisdom of the masses, a question:
Fortunately or not, the problem which had been very intermittent (usually only after several days of sitting) has now become rather regular, now that I have a Digitool to play with:-)
After startup, the bus (91 syncro) may idle fine for a bit but then begin to sputter (lower idle). driving is impossible (no throttle is accepted - only kills it more) Shut down and restart results in temporary perfect running (30 sec?)  then more of the same.  After several cycles of restarts and high revving acceleration (during the short grace period) the problem vanishes for the rest of the day's driving (at least until recently,  now it may have fits after every shut off even if for 10 min- IE still warm)  So what of the Digitool?  Everything but the Oxygen sensor reads as they always have.  Recently, I had a chance to monitor while the bus was having fits regularly after shut off (after the 30 second grace period).  After a 45 min highway drive we shut it off for a half hour then tried to leave.  The oxy sensor was reading 6+ volts and slowly dropping while the bus sputtered.  Slowly the volt would approach the expected 0.6 range and begin to fluctuate as usual (0 to 0.6 volts) and the bus fit would be over.  This would repeat itself  to varying degrees.  This problem seems to be associated with rain.  The Oxy is new (10K mi./Bosch)  and when not having a fit the oxy seems fine and the bus runs fantastic.  I recently removed  the ground strap to the left head and cleaned and replaced during a real bad fit episode.  
 What's up?
Nat
Seattle