Looks like it doesn't want to make it easy for you.
So if injector #2 is new but the rest are old, maybe you could try swapping the injectors and log for misfires again to see if the problem follows the injectors?
Apart from that I would also suggest to monitor/inspect the air intake. Intake manifold issues (blown gaskets, air leaks, bad valves, sticky flaps) often cause misfires. Most of them, especially sensors and valves, would show errors though AFAIK. Also monitoring the fuel trims might give you a clue about the issue.
BTW did you inspect the old spark plugs during removal?