You need the air/fuel messuring position sensor.
I'm certain about this cause I'm sure the odle speed cylinoid was probably
replaced once or twice in an effort to fix the problem but it didn't, am I
right so far?.
I'm sure you've seen your engine with the air filter off, well right underneath
it is the big round 3inch diameter plate, as you excelorate the vacuum created
draws down that plate which opposite end is connected to the fuel distribitor,
the two are connected by a piviting arm.
Tp make a long story short cause I'm sure you don't care all that much about
The piviting has it's own sensor, the cars computer wants to know at any given
time hwta position that plate is in.
When you let off the gas pedal the idle speed system is suppossed to kick, and
you and the dealer both assume it isn't, well the problem is it is kicked in,
allowing too much air at the moment that you let off the gas pedal, the sensor
is not letting the computer know that the car is at idle.
If you disconnect your idle speed cylinoid for a month you will notice that car
is not cutting off anymore.
To fix this you need to replace the entire housing that mounts the fuel
distruibitor, the housing includes that plate in question, this is quite
expensive, I think $ 700 in ports, Bill correct me if this figure is wrong!!.
3 years ago my parts supplier carried just the sensor, it was a bit tricky to
install it, but only $50.00.
you can go out and get some other opinions, but nothing will fix it but the
sensor, good luck and keep us posted.