the RBS 1R600 valve replaces the standard valve in the integral resevoir pump and reduces the output pressure, it doesn't change the flow rate. M2 racks need a lower pressure than a Saginaw steering box setup.
You can do this modification on a Saginaw pump yourself if you want. If you remove the valve -it's behind the output union on the pump- and insert extra shims behind the bolt in the base of the valve body, it reduces the pressure on the internal spring that's behind the bolt, and therefore reduces the output pressure of the pump.
As well a s being a good mod for M2 racks, it's a good conversion to get some "road feel" out of the Saginaw P/S conversion for AD trucks; I have reduced the pressure by this method on my truck which has improved the road feel, and may reduce it again when I get the time.
HTH, Stuart.
