Sounds like....
A slow responding IAC.
You see as you turn the wheel when the car is stopped you are putting additional strain on the power steering pump, which in turn puts more strain on the engine.
Normally, the computer would detect the slight change in idle speed and open up the IAC to respond to the increased load. A similar thing happens when you turn your A/C system on.
Now if the IAC is gummy or old, then it won't respond quickly or at all.
That would be the first area that I would be checking......