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...
"Is this normal? I have never experienced this in any other vehicle."
No! That is NOT normal. I would not touch it other than to take it to an authorized Ford truck dealer and explain your issue ASAP. It sounds like a pressure control problem which isn't anything you can (or should have to) resolve yourself. It could be as simple as a loose belt, but IMO you would have other issues also if that was the case. Since you are under warranty, let it be Fords problem.