WAIT!   ... i'd said:
now the 'fast idle' on a pre-86 engine is totally different. there the
bypass air is regulated with an electromechanical device that has a bimetal
strip that lowers a disk over the bypass orfice. a heater wrapped around
the bimetal controls the 'warm up' time on this and one can see an authentic
fast idle with this system. no ECU input.
***

before Mr. Skerbitz corrects me, (and he WILL!) i'll correct myself.  the
Digijet system DOES have some form of electronic idle control... the
infamous box on the firewall with 2 plugs in it.  it stabilizes the idle by
advancing or retarding the timing (only at idle) to give a somewhat uniform
idle speed.  same thing should happen as in the Digifant... pretty much even
idle speed regardless of conditions.  in theory :)

there.  i feel better.
-dan