That code is set when an injector has a balance rate below -7 mm³. I'm not saying you are wasting your time verifying the wiring, but that would be setting a circuit code. This is something mechanical with the truck. I would try moving that injector to another hole and see if the problem moves with it. It could just be a matter of the factory calibration codes throwing things off. Aftermarket injectors typically don't come with new codes, so I like to make the codes all the same to prevent them from causing balance anomalies like this.
well i didn’t see chevy1925’s advice till after i adjusted the flow rates. local shop owner let me use his snap-on scanner, made it real quick and easy. i checked balance rates with the scanner right after and #2 was still at -4 and then slowly climbed to -7 which set the code.
i shorted the fuel system last night and idled through a gallon of 1:1 injector cleaner /diesel. didn’t seem to have any affect on balance rates.
today after adjusting flow rates i took it out for a good ol italian tuneup over local mtn pass. the thing gets up and GOES! anyway these are my balance rates after in the driveway. i let it idle for a good 10 min and no code, rates are solid at displayed values. first pic is in drive