Glen,

I would check to see that the fuel pressure is correct.  The fuel
pressure regulator values are 29 Psi with vacuum connected and 36 Psi
with vacuum disconnect. As I recall.the fuel pressure should remain
above 20 psi for ten minutes after you turn off the ignition, The fuel
pressure leak down could be either the regulator or the fuel pump as
both need to work.  Leaking fuel injector could be a another leak spot,
but the engine would crank up with a chugging cylinder, which you didn't
mention.

If your getting fuel pressure, then read the voltage signal at the O2
sensor, green wire + and the ground to the frame.  The voltage should
fall between .3 volts and .7 volts.  With your plugs indicated a leaner
mixture, my feeling is fuel supply is a good possibility. You should
double check that the timing mark is moving with engine speed as well.

Many suggest that anytime an issue comes up in this area, it is wise to
clean all grounds.  Additionally the coaxial cable that carries the O2
sensor signal to the computer is also to be checked and replace if need;
Microphone cable is a good substitute.   You could have open 02 cable
and just have lean open loop set up on your basic fuel injection.  This
is often a rich indication, since the afm wiper spring weakens with age,
but a lean condition is a possibility.  The proper setting is two adjust
the wiper spring until you get .5 or so volts on the O2 sensor with the
engine at 3000 RPM.   I would add that all adjustment must be made on a
warm engine.  BTW the idle control unit issue is just for cold idle and
is not a warm idle issue, with the possible exception of the power
steering and a/c idle compensation systems if they use idle air, or a
map setting in the ECU.

Sincerely,

Mark Keller
91 Carat