The pump could be a bit sticky, not lessening the pressure as the speed(of engine=road speed) rises, so might be worth putting in some wynns power steering system conditioner, will also help other aspects of it as well.
Maybe it's because it is a quick rack, they do take a bit of concentration especially if new to cossies, but generally very well weighted, I also find them too light at speed, but used to it now.
tabetha