Find the fuel milage you are getting before replacing the injectors unless there is another reason to do so. On these older cars they might have been changed out or recalibrated and checked at some time in the not too long distant past.

All my injectors on average appear to be still pretty decent. If they have been out and checked over the years I have no ideal. Mercedes recommends they be checked about every 100k.

With a little luck they are done at least the once anyways when some other owner had the car. If performance and fuel milage are still good with no excess smoking etc or nailing issues I tend to leave them alone.