I have been noticing the exact problem with mine (I think) for about a month now.
the engine never feels like a misfire, just like the fuel gets shut off, (or vapor lock in the line) while accelerating between 4-6k RPM's.
It only manifests itself when the fuel tank is at 1/2 tank, or less. Once I fill it up, it goes away. also, the lower the fuel level, the worse the occurences.
Tried the Techron and replaced the fuel filter, with no luck. Currently it's at Ford. I saw the technician drive it in from his test drive and pull it into the bay and raise the hood, so I know he felt it.
Unfortunately, he had the "Bubba" look when he got out of the car and after looking on OASIS. I'll let you guys know what they find out.
BTW, I put in a K&N last year, but I can't remember cleaning it yet (only 19k miles)
Later,
David
