I have an 07 Ford F-150 5.4. I have replaced all plugs and coil packs, VCT sensor. Why does cylinder 7 keep miss firing

 

If it was all only that easy.
You might want to start with a compression test. That should give you some idea where to continue.
If a problem with valve spring, or cam lobe , the results should help to either confirm or lead to addl tests to determine cause of misfire.

 

Try swapping fuel injectors with another cylinder and see if the code follows the suspect injector.