I am not sure about that particular car but some cars have a electrically switched valve on the power steering pump which lowers the pressure for higher speed t

I am not sure about that particular car but some cars have a electrically switched valve on the power steering pump which lowers the pressure for higher speed travel (less responsive). You may be able to get "some" control just by disconnecting this (assuming it is there, my 93 Mazda 626 had one).