2003 5.3L Silverado Fuel Pump

I have had a problem with idle being low at 500 RPM's in drive. It drives fine at driving speeds then suddenly has started idling rough and the engine light started flashing. I then checked for any DTC's and kept kicking out P0300 DTC which is a random misfire. I changed spark plugs checked the plug wires and has great spark from all cylinders. I then started on the fuel system by changing fuel filter and nothing seemed to be working. I was about to change the Fuel Pressure Regulator and took a fuel pressure reading first. When turning the ignition on, it jumps to 60 psi. Then I started the enigine and it ran at 50psi and when reving the enigine it would go up to near 60 psi then drop to 48psi. What I did not notice at first is when turning the idnition to the on postition it would start out at 60 psi then drip to 9 psi within 1 minute.

I assume this would be the fuel pump nd not the FPR with it not holding pressure with the ignition on. anyone have any problems with the fuel pressure dropping to 9 psi with ingnition on?