Answer: You don’t say what kind of pump you are using, but I’m not sure if it even matters. The pump pressure could be the problem, but there are a few things that I would check first. You say that the front end has all new parts. But does it really? Have the tie rods (inner and outer), upper and lower ball joints, control arm bushings and wheel bearings all been checked or replaced? Excessive wear in any of the front end parts could cause the symptom that you are describing, and high pump pressure will only exaggerate it. If all of these parts have been checked and /or replaced, then you will probably want to look the at pump itself, or the pump pressure, as a potential source of the problem.
Lowering the pump pressure will lower the level of power steering assist that will be available at all speeds. Since power assist is not really needed at higher speeds, the pump pressure is usually set to provide the proper amount of assist when the car is at low speeds or standing still. Depending on the type of pump that is being used, you can reduce the pressure by changing to a larger pulley or using a kit from Classic Performance Products (www.classicperform.com). It would be wise for you to have the pump and the pump pressure tested before haphazardly spending money on modifications and repairs. Changing the power steering pump is not a particularly difficult job, but diagnosing any pressure related problems is probably best left to the professionals. These pumps operate at pressures of well over 1000 lbs. per square inch and flying parts can be lethal