06 5.4 w/ misfire cyl 1. Swapped coils, reset code , misfire on cyl 1, Also picked up rich on bank 1. and O2 sensor 1 biased and stuck rich . Replaced all 8 plugs , reset codes. Cranked great , ran smooth for about 5 min and it started all over again. Misfire on cyl 1 . Rich on right bank. O2 sensor 1 biased and stuck rich . Removed coil while running and good crisp popping heard.

 

I would say you need a new o2 sensor.

 

Swap fuel injectors. Post exact code numbers.