Thanks for all of the help with the A/C pressures. Now with that behind me, I need to resolve the second major issue on this truck, the idle.
It's more of an issue when the engine is first started, doesn't have to be a cold engine. When it's idling without stalling, the truck's lucky to be at 570RPMs.
Things I've checked and/or tried:
Replaced IAC - went back to OEM since problem wasn't resolved
Cleaned MAF sensor
Replaced O2 sensors with Bosch specific fit
Sprayed around intake with starting fluid to determine if there might be a vacuum leak - no change at all in RPM and I doused it with 2/3 of a can.
Double checked PCM C1 blue pins 20 and 57 to constant +12V
Verified coil pack side and plug side are all fully seated for all 8 wires
Checked fuel pressure: KOEO = 54PSI, KOER = 44PSI at idle and 54PSI when throttled moderately. Also disconnected vacuum line while running and it came up to 53PSI from from 44PSI.
I realize that the fuel pressure is low, but I don't know if my gauge is accurate. Tried to rent one from Autozone, but all 4 stores near me were out of stock.
BTW, no codes in the computer per my OBD II scanner, but the tuner also just told me that it won't throw P0300 misfire codes, he believes because the fuel tank level isn't being sent to the PCM.
Youtube videos of how it sounds:
https://www.youtube.com/watch?v=Z9LVq95IQTA
https://youtu.be/BPxKjJetD0Q