Too much flow will mess up the spool valve and/or make the steering too light. Bypassing too much fluid with the restirctor will cause the fluid to over heat as well as aerate. Making the power assist sporatic at best.
I had my pump rebuilt by ARG to match the flow of my rack. They also fluted the vanes so they would not foam up the fluid.
They changed the torsion bar size in the pinion valve to improve the feel.
Here is a link, go the the middle of the page
http://www.agrperformance.com/Hot-Ro...erformance.htm
All of this may have been done to your stuff, but this is what I had to do the the yellow car when it was first completed many moons ago.