Not sure. I just installed new injectors myself in June...and I too think about this equal flow issue.
I'm going to ramble on a bit; Mine is at +7%...and I can only think it is due to wear. Only, I replaced all of the fueling bits; both pumps, both sensors, control module, and injectors. The PCV is good, the MAP shows between 272 to 280 g/s each data pull, and the thermostat is new so I doubt the temp is triggering a fuel additive. But I haven't checked compression since before I rebuilt the head. Even though it was smoking from the pinched ring in 2016, but it still had 191 to 195 psi in all four cylinders before the rebuild of the head. I can't imagine it is worse now with the rebuilt head and new rings. I've smoke tested it and all is sealed. I hate to settle, but I almost feel I need to settle and say it is wear. I've replaced the B1S1 O2 not so long ago but this could be causing it. I know coils can fade. All four were replaced at one point due to an open campaign many years ago...and I replaced one in 2013 or 2014 when I ran the DM tune. Maybe it just needs four new coils. I just want better mileage like it once did. I have to baby it all the time to average 28 mpg right now. If I drive it how I normally did in the past, it barely makes 23 mpg now...and when I drove it however I wished to in the past it would average over 27 mpg.
If I were seeing misfires in a single cylinder...I would have its new injectors tested. I may just try new coils and a B1S1 O2 to see if these change the trims. I can tell you what made the hugest difference in my trims was a small leak I found at the MAF seal in the p-flo intake during a smoke test. The leak was minor, barely saw the smoke coming out, but once sealed the LTFT off-idle went from near 18% to below 8%. Maybe I need to smoke test it again just to double check it all.