One odd possibility, if it ONLY stalls with a lot of steering input & NO throttle input at the time.
There is a pressure sensor on the P.S. pump. At high steering loads it tells the computer to increase idle speed to prevent stalling (rpm might not actually go up, the idea is to give it a bit more throttle with the IAC to prevent stalling)
So, if that connection is unplugged by chance, or the sensor isn't working right anymore, you would get a stall when steering sharply with no throttle applied - as in tight turns or parking lot maneuvers...
Of course any OTHER issues that cause low idle or poor running may be the REAL problem - just wanted to throw in this possible direct cause if all else is OK.