I think the only real way to proof test frp sensor would be insert a suitable test gauge to the rail. I think tne only equipment that properly allows this with the engine running is bosch but I dont see what harm it can do by removing an injector pipe from the rail, disconnecting the injector electrical connector (if it will still run unplugged) and conmecting the sykes crd test kit to the rail.

Its 1700bar raited so can't see this being any different to testing direct at pump.

At leadt this way your scantool will show what its seeing compared to actual pressure.

I'm sure Mark Carter will correct this if its wromg or more importantly dangerous.