What causes a 2002 5.4 to idle rough?

I have a 2002 F-150 with a 5.4. The truck idles rough and shakes going between 40-50 mph. I read the codes and it has a cylinder misfire in 8, and fuel is too lean in both banks. I have replaced all 8 injectors a few months ago, along with exhaust manifold, and manifold gaskets. In the past year I have replaced all 8 spark plugs and boots, they are gaped properly. I am thinking it could be either the coil pack in cylinder 8, or a oxygen sensor, or perhaps both. Any assistance would be greatly appreciated.