On one of my cars, I removed the injectors to have them cleaned & blueprinted.
The difference was amazing.
I also remember, when I took Computerized Engine Controls 101 ( looooong time ago ), the instructor suggested, if you ever buy injectors over the counter, to take a DVOM with you & check the resistance of each injector on the spot.
The idea was to match them, since there is usually a no-return policy on anything automotive electrical.