It matches the symptoms for sure, just a bit flummoxed about how cleaning the HFPP would make the FPRV go bad, unless the total loss of rail pressure via uncapping the lines made it give up the ghost, or a small bit of debris made its way into the line and clogged it.
Did you replace the screen in the FPRV or the HPFP? You could try to remove the screen from the FPRV and see if it changes.