The basics are all good, plugs, filters, etc...
I see ford has a tsb out for it now, involves an engine flush with some ford cleaners. I did it once and it may have helped, it was tough to tell. tsb says if that doesn't fix it to try it again, so I'll be doing another soon.
If that doesn't fix it whats next? A few years ago I did the tsb because of the oil leaking into the intake. That tsb and the ping one both have steps I cannot do at home. They both involved an update for the PCM, maybe call my ford dealer and see if they'll do the PCM steps for me?