P0304: Cylinder 4 Misfire Detected got this code. This fuel pressure regulator

why change the regulator? plug been checked? wire or coil been tested,depending on engine size?.. if 4.8L or 5.3L and you have no testing equipment,try and swap #4 coil with #2 coil,clear the code,start it up,read code again when the light comes back on,see if the error moved to #2. standing in front of the truck #2 is the 1st one at front on passenger side..#4 is the 2nd one from front,same side>passenger side..post results.