I have the same issue with my 2001 5.4 with 63K miles, but only misfires intermittantly when engine is hot and with applying slight accleration. I also have no check engine light. The misfire finally showed up on cyl 5 & 7. Had the plugs replaced, the mechanic put in Autolights problem got worse. Took the truck back they installed Motorcraft, which someone on this site recommneded, also replaced all the boots. Problem is still there but truck runs better and it takes more time (gets hotter) for it to show up. Also had the injectors checked, all good, have dumped heet in the gas tank thinking maybe water in the gas, and changed fuel filter. Don't know what to check next. May go for the EGR valve/sensor.
Please write back if you find anything that works.