I would say you have a pocket of air somewhere that is not moving. Get yourself a gauge/hose assembly to connect to the fuel system Schrader valve connector on the RF to see if you are losing fuel system pressure. I installed a Kennedy Lift pump and added a Mega filter assembly about 3 months ago and bleeding ALL of the air is paramount to firing it off.I have my batteries getting load tested right now. Im gonna pick em up in a few hours if good and maybe try looking for a air leak on the low pressure side? from the filter back to the tank. Will it help to prime the filter housing still and spray some soapy water all over the rubber lines?
Could Fuel pressure regulator be bad and not show any codes? If I have enough rail pressure, then it has to be a leak on the low side or something electrical right?