i would say that the pump is pressuring the system too much and then it's kicking out again

not sure what could cause this as it could be a blockage, the pump being fubar, not enough oil in the system, a sensor, or anything else

the proper gauges have 2 gauges to measure 2 different things from the 2 different connectors so perhaps you could try to connect it to the lower/high pressure side and see if that's any different?

not sure if they have the same fittings though