MAN Engine

Part of the reason for pulling the injectors, is so you can get them out! If you wait too many years, you're going to have to pull a few heads because a few injectors won't come out. The other reason being is that it's always good to check them and go through them. The pre common rail engines also got pretty smoking at slow speeds if they weren't done on schedule.

Anything that he can see on a laptop can only confirm that the governor (which is the one and only electronic bit in your otherwise mechanical engines) is working as it should.
But there's no way he could check anything about the REAL injector behaviour - i.e., opening pressure, nozzle conditions, spray pattern.
I'm not saying that there's anything wrong with your injectors, but pretty sure neither you (and me!) nor the best MAN engineer on earth can know for sure without pulling them.
On top of that, I fully agree with everything CJ just said.