I would also try a different reg and see if that helps. I bought a CP and had similar issues, turns out the regs can come in two different pressure configurations, depending on the piston. No one really seems to know about this for some reason
That might not be the issue if you have one of the newer regs, and with the pressure drop you are describing, but could very well be a factor.
If it turns out that's the case, ANS is the only place I've found the replacement pistons http://www.ansgear.com/Paintball_Reg...arts_s/316.htm