[rhandwor]

I didn't know buick used a choke in 1993. I think you have throttle body injection. Two injectors on top of the throttle body. The otc is reading the temperature of the computer temperature control. This has two wires ond should be on the intake close to the upper radiator connection. If you installed a new 195 degree thermostat and it is working change this unit.
I changed one on a Chevy pickup that was bad and the mileage doubled.
A cracked exhaust manifold close to the oxygen sensor will give you a very rich mixture. Neither problem usually causes stalling. Spray carb cleaner along the intake manifold and the base of the throttle body. A bad air leak will cause stalling. A stuck open egr will cause stalling.