01 2500 6.0 misfire at idle when cold P0300

[teg_b18c1]

I have a 2001 Chevy 2500 2wd automatic 6.0 v8 work truck. The problem is today my truck started idling rough ONLY while the truck was cold in (closed loop on ecu) the truck had miss fires P0300 on many cylinders mainly 1,7,8. The motor was idling VERY rough and the check engine light was flashing. I hooked up a snap-on scanner and looked at the missfire data. I checked the spark of all the coils by pulling off the sparkplug boot while the engine was running. The part that has me confused is that I could unplug any of the 4 driver side coils and it would not affect the rough running engine but if I unplugged any one of the passenger side coils the motor would die. So their
must be a fuel delivery problem with the drivers side of the engine.

I was driving it to my local mechanic to look at it and as soon as the motor got to operating temp and the ECU switched to open loop the check engine light went off and it started running and idling great

I replace the fuel pressure regulator no change. The truck has new plug wires, spark plugs, alternator, recently cleaned throttle body and IAC.

I am stumped. The only thing I can think of is O2 sensor.