skipping vehicle

Having an issue with a 2013 maxxforce DT truck was originally towed in as a no start found high pressure oil pump was no good. replaced pump and started up also replaced EGR cooler for complaint of loosing coolant after that portion of the job road tested to get air out of the high pressure oil system. engine is still skipping not sure if this was a previous issue our one caused by what we did. found that injector #6 was not rattling when triggered in KOEO test. replaced #6 injector and truck ran great road tested after idling in the yard and it began to skip again when i run KOEO injector test 6 is not rattling as it should i also swapped out uvc harness with no change harness wiring checked out OK also swapped UVC wiring with injectors 5 and 6 and 6 will rattle when #5 is supposed to