How much power steering pump pressure should I have?

[builttodrive]

I have a 70 mustang that is using a power steering rack conversion and that uses a GM J car rack assembly (cavalier, beretta, etc.) I am using a GM type II power steering pump that came with it. I also have Hydrtech, hydroboost brakes on the car. I get a small amount of feedback in the wheel when I use the brakes and steer at the same time a low speeds (RPM). Hydratech indicated I probably need a little more pressure. I pulled the valve out of my pump and I see it has just one shim (washer) on the valve indicating I should have around 1,200 psi from the pump. Should I remove that shim and that would make it around 1,350 psi?