If it makes a difference (on where its reading the pressure from), the gauge is between the pump and the filter. I have a new filter but it requires some hose fittings so haven't been able to test that yet.
It is running a VL pump and I took it off and replaced it with another second hand one which I pulled out of a perfectly running VL, so no reason to think there was a problem with it, but it has just sat around for a while, so possibly could be the pump.
I may be wrong, but if I crimped the return line, and pressure stayed at 30psi, wouldn't that mean the return is fine and there is a problem with the fump or something??
I'm a little confused...