I am refreshing the engine (changining out vacuum/fuel lines) and cleaning the engine, painting etc. While stripping down the engine i was looking a the injectors and they look a little rough -seals a little chewed up etc, nothing major but I started wondering. Is there a way to tell when to replace the injectors? I mean the car had a hard time idling and running smooth before but not sure if was them or not.

Change out the seals as they make a huge difference. You can test the injectors for their spray pattern and see if they are toast.

Geoff