Expect to get the pressure around 500 psi with some simple mods. That's where mine runs at right now. I kind of live by the "Do it right or don't bother" motto, so naturally I went for a PPS Stab on mine. I took the venturi part out of my bolt, raised my FPS by about 20 fps. It just unscrewed with some force, I don't know what the bolt is like in yours. I also have a lightened valve spring to increase the amount of air released, but I have not yet modded the valve or valve stem.
Otter SC Customs used to have a nice spyder page, but the site seems to have died.
You can still view the info through Google Cache. Low Pressure - F.A.Q. Project - LP