2003 Mercury sable stalls under slight load (going uphill) turn on air conditioning, car shakes and misses very bad and dies. What is a good course of action?

Thank you tennis shoes, more to my efforst: I had a code found po191, after reading and replacing the fuel sensor located front top left prior to the fuel rail it is better (has more power) still misses, less now than before, with the warmer weather I drove it and turned on the ac, this drastically increased the miss. Reading your above comments ( not getting ac or psps commands) believe there is something with that. Replacing the fuel regulator/sensor did make the engine light go out. Still in need of a solution.