Check engine light came on with noticeable what I believe is fuel injector tick
on 2005 Ford Expedition

Also note slight hesitation/miss on acceleration on mild incline.

Scan test is needed to find out why the light is on first thing! Save all the guess work.
1 more answer
If you believe the fuel injector is bad you can unplug one connector at a time from each injector. If there is a change in the idle or it runs worse/rough the injector you unplugged is a good injector. Plug each injector back in after checking it. If you have a bad injector the engine will not change idle when unplugged. Of coarse the engine must be on when checking these.