Digifant II system, inline four VW.. 1.8 liter head...

     This motor has normally started up and 'hunted' up and down for a
second or two, then settled into a perfect idle...all without any
accelerator input.   Just in the past few days, I've had it go back to that
"hunting around" after my first tap on the gas pedal...and almost
die....then behave perfectly normal again...Just for a second or two when I
get off the gas and only just after I start up and maybe back up to turn
around or something...or blip the throttle as a habit...it goes back to
'hunting around"   like perhaps the throttle switch is going out? or the O2
sensor could be fouling up?  I may be imagining this but I think it may be
taking 1/4 second longer to fire off, too...maybe half a revolution more
before it starts...Could be imagination it's not much longer if any....

   I have been operating with a leak in my exhaust system just upstream of
my O2 sensor...and this causes some exhaust 'popping'  especially during my
first few miles until the vehicle warms up totally...Likely it is sucking
oxygen into the crack and the unburned fuel is igniting in the exhaust pipe
on drop throttle.   I don't think the two things are related...I have been
running cracked now for about a year without anything other than the
poppity pop pop when I coast downhill when the engine is not warmed up...

  Anybody want to guess what's beginning to change  this motor's previously
sterling start up and idle behavior?

  Thanks, Don Hanson