2006 Ford Explorer rough idle & low power

Based on what you've checked already, the injector is the logical suspect. The best way to tell is to swap it with one from a different cylinder, erase the fault code, then see if a misfire code sets for the cylinder you moved that injector too.

Another common problem with Fords is plugged EGR passages but that usually involves the V-8 engines. Ford dumps in a calculated amount of inert exhaust gas, then they assume it is going to go evenly to all the cylinders. As those passages become plugged, those cylinders run fine, but the unplugged passages send all the EGR flow to the last one or two cylinders. That's when the only good cylinder misfires due to too much exhaust gas.