Fuel injector diagnosis help

[Briggskid987]

My buddy has a 99 F250 SD with the 7.3L in it with around 100k on it. We took it to an independent shop and was told that 3 of the injectors would need to be replaced. They said once they had it apart they would go ahead and pressure check all 8 of the injectors and let us know on the condition of all of them.

We also took it to the ford dealer for a 2nd opinion and they ran the injector test on it and told us the injector wiring harness was frayed and mangled causing the problem and that none of the injectors were bad.

The independent shop did the diagnosis for free and we were told they put it on there machine and checked it. They did not do any dis-assembly on the engine or anything like that before comming to the conclusion.

My question is would it be possible that because the wiring harness for the injectors was frayed and damaged, would it be possible for it to show up as bad injectors on a different test (possibly a less thorough test)?

I have used the independent shop in the past on many occasions and 65% of their work is on light duty diesel trucks, with the other 35% being in heavy duty truck diesel repair. I have been fully satisfied with their work and prices and have never had 1 issue with anything! They have been in business for over 45 years and get great recommendations from dozens and dozens of people and parts suppliers!

I'm just trying to find out if they were taking my buddy for a ride or this was a mistake.. IMHO, it would seem likely that is was a mistake, similar to diagnosing a spark issue on a car with a bad spark plug wire.
Thanks for any insight on this!!