Seems like he addressed this issue already. "decided to replace both fuel pressure regulators and both fuel pumps with walbro pumps in the cool fuel housing, I cleaned the pickup screens while in there. Fuel rails were cleaned when injectors were cleaned." Did you also replace the low pressure pump?
The misfires the computer registers are imperceptable. Once it reaches a certain percentage of the total its considered maximum number of misfires exceeded. This level was set very low on first gen catalyst motors in order to prevent damage to the the cats. My 2011 377mag had the same problem. I...