tough start, runs rough, low power, P0266 code, #2 does not click on buzz test

First time 6.0L afters 20 years of 7.3s. Wife's uncle called Sat said F it, you want this 6.0L come get it. P0266 keeps coming back. Buzz test on 6.0 must not buzz but clicks each. It skips #2. In reading folks point to FICM a lot. Is it common to have a FICM drop firing just 1 injector? I read an idea to swap #2 & #4 injector connectors and see if during the buzz test that the FICM firing #4 will click #24. Will try that next. Am I on right track or any other ideas before I move ahead with pulling the injector if the connector swap does not click#2 with the #4 FICM signal?