I have a 01 F250 5.4l with 70k. I have replaced the spark plugs coil packs and the injector on cyl 7 and still have a misfire on that cylinder. Goes away at higher rpm. Some days you start it and it runs great then it will start misfiring and running rough it does not throw a check engine light at all

 

Did you take any compression readings to compare between cylinders?
Are you thinking #7 is on the passenger side or driver side?

Just a thought. I found 3 plugs had electrodes eroded; stumbled when accelerating but would not stumble when in a lower gear.