At full speed you do not need the steering assist; frankly, they are suppose to be setup so the faster you go the less assist there is. Using the Spyder mr2 pump, which he is, it comes with the assist sensor, as he already mentioned, using the older MR2 pumps, like I am, one needs to run them to a pressure switch, like the preludes already come.Why? Either delete it or use it. If you don't delete it, its not good to turn it on and off. If you delete it you will get used to not having it after a month.
Having the steering hooked up to an on or off switch works, as Wing has done(without issues mind you), so there are options there, but I can say that not having PS can be a bitch when trying to parallel park or put the car onto the dyno.