i'll try to help.
first, unplug your oxy sensor and see what the voltage of it is in series-
it should be about .5 volts when cold and change a bit when warm.  That
could save your some bucks right there.  I bet this is it btw.  If your
oxygen sensor has been bad for a while, then your catalytic converter is
probably clogged- hence the stalling when driving. I bet it starts fine
when cold and goes down hill when warm, right?   I'm not sure how to see
if your catalytic converter is bad besides replacing it... or as a
extreme and very very very temporary fix- bash it out.

If those are ok, check your Temp II sensor. This is the sensor that is
blue (for me it is)- it is the one that faces more back than the other
one.It is onthe left hand sided of the engine near the fan belts.  This
should be about .22volts when warm.

If it runs like crap all the time- even when cold- it could be the
throttle stitches. These are the gray switches located on the top of the
engine adjacent to the throttle cable.  They should be closed when you are
at idle and not touching the gas and at fully open.  just as you touch the
gas, they should turn off.  you can again check this with your handy
voltmeter.

DId you say your AFM is new or what? If it is old, then carefullly pry off
the black cover and clean the wiper with rubbing alcohol or the like.

By the way, where are you located? I'm sure if you are desperate, a handy
listee in your area could help some evening for beer and or dinner. I know
i would :-)

Hope this help. Email if you have more questions.
-matthew
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Matthew Pollard             http://www.uidaho.edu/~poll7356
Dept. of Chemistry               http://www.chem.uidaho.edu
University of Idaho                   http://www.uidaho.edu