Hey Dirk, I think 1000 psi is still too high. What rack did you decide on and install? The Mustang II racks need 700-800 psi as I understand. If yours is rated for higher psi, its not a Mustang II type. You have at least two choices. Heidts can sell you an adjustable valve that you mount in-line permanently, this is a precise way to dial in exactly what assist you want for road "feel". The other option I PM'd you about is to use a shim kit on the GM pump HP valve, and reduce the pressure that way (I went this route). The down side is you may need to try different numbers of shims before you get the road feel just right, which means a few messy drain and fills of the system. The other downside is you'll build more heat in the PS system with excessive head pressure with the valve mod. Which means shorter component life without adding a PS cooler. The Heidt's solution has a by-pass line that sends excess fluid into return line to keep PS fluid temps down, thats their statement, but I have never tried it. Perhaps others who have done this can chime in here and tell us more pros/cons of the heidt solution.
read this link for details
http://www.heidts.com/pdf/art1.pdf