Just for clarification on the Duratec side of things, you need to get a double-platinum plug to avoid missing/bucking problems, and stick with OEM spec plugs. The Autolite part number (the Motorcraft equivalent) is APP764. I know about this problem first hand; I had missing problems under high load at highway speeds (80+mph) only. I had done a tuneup before learning of CEG and used really crappy plugs that claimed to be OEM replacements. After installing the Autolites I've had no problems.
Back on topic, congrats for finding the fix to your problem. I know how relieving it feels to solve a problem that's been bugging you for a while.
