1987 Cadillac Fleetwood (De Elegance) Stall problem, help

I have a 1987 Cadillac De Elegance with 38,000 miles on it believe it or not. Recently it started dying when I come to a stop. It only does it after the engine has warmed up a good while, never in the first 10-20 minutes.
Sometimes when I turn the wheel at idle, othertimes simply dies when I stop. The GM dealership has replaced an idle motor, somthing on the AC that adjust the idle when it kicks in and I'm tired of throwing $$$ at it if they don't know what is wrong which is obvious now. They have also set everything back to factory specs whatever that entails.
The car is in excellent shape otherwise and with the super low miles I would like to hang on to it although I did buy another car that I could depend on for everyday driving.
Any help on this is appreciated. remove the "at" in the email address to reply directly or reply to the group. Thanks, Ken

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