Little update on this issue. Finally found time to get this thing in the shop late last week in-between customers trucks.
I threw in a new motorcraft crank sensor and the problem initially got much worse. While free revving it began having this issue at a much lower rpm, like around 1800 to 2000. I then removed the sensor, inspected it and the port where it goes, and re-installed it. The issue then moved back to the 3000 rpm area where it had been previously with the old sensor. Soo with that in mind, I made the assumption that maybe I didn't quite have the sensor completely bottomed out in the port and that for some reason the crank sensor is losing signal at higher rpms. With that in mind, I took a file and filed some material off of the stop on the old crank sensor soo it would sit closer to the crankshaft tone ring. Well doing that all but fixed the issue except for when the truck is below 140 degrees coolant temp. Anything above 140 degrees, it pulls to 4k rpm as smooth as glass, runs and drives perfect. I'm assuming that the distance between the sensor and tone ring is still slightly out of spec, and as soon as it gets up to temp, it expands just enough to work the way it's supposed to. Why it never threw a sync code or a crank sensor code is still a mystery to me but at least I can beat on it now like God himself intended 6.4s to be beat on. If anyone else has any theories, I'm all ears. Thanks for the earlier suggestions and help.
