My brother has a 05 f350 6.0, it started skipping about a month ago so i put the ae on it and got p0266 code. We replaced all 8 injectors with 175cc ones. He wanted to upgrade anyway, and it seemed to run good for a couple hundred miles but started skipping again and throwing p0266 code. The buzz test passes all cylinders and I unplugged injector 2 while running and no change in the skipping but I can hear the injector stop firing, plug it back in and hear it start back but no change in motor. Where do I need to start looking now? I'm really tring to figure this out for him and will appreciate any info.