High Fuel Pressure

Been having a problem with a 1996 XJ 4.0. It runs fine until it is warmed up, and then it starts hesitating and has no power at operating temp.I replaced the fuel pump and the filter on the frame rail to no avail. Just bought a gauge today to test fuel pressure. With the key in the on position it sits at 48psi, but when I start the jeep it jumps up to 60-62psi and the gauge jumps erratically. Is this pressure too high? My other XJ runs at 49psi.

Fuel pressure does sound too high. Can't recall but what is the "regulator" setup on a 1996? Is it separate from the pump? I'd be a bit suspect of that piece of hardware.

A field service manual would provide you with comprehensive fuel pressure testing to help you isolate root cause. You've got the gauge; I'd find an FSM and do some more testing.