I have noticed that at idle, the power steering assist is minimal. Increase the RPMs and the assist improves. Where this becomes a problem is on curves when I increase or decrease acceleration, as the...
There is supposed to be a system in the power steering pump that makes it behave pretty much the same throughout the engine's operating band. I suspect that it is non-functional. Start by telling the service person that the power steering is not working well when the engine is at parking lot speed. That will get them pointed in the right direction.
If he says "They all do that." Then get a factory representative to try it out.