Could be other things on that cylinder as well. Best to take a spare injector and substitute it on the suspect cylinder. Then if it is just the injector you know for sure.

Otherwise a bit of a crap shoot in my opinion. Or swap locations of the same injector to see if the problem moves with the injector.

Just loosening the injector line and seeing no difference does not prove it is the injector. It could just as easily be a valve or an issue with the injection pump for that cylinder.