Most of our trucks have this... as a matter of fact, most 5.4 engines in general have this. This is nothing that will hurt the engine, and there is nothing that will fix it. If your truck had this problem, it was nothing to worry about - it would have made it for the long haul. My dad's 5.4 has had this since day one, and it now has 130,000 flawless miles. My fiance's dad also has the same issue and he has 170,000 miles.
Sounds like you may have given up a perfectly good truck.... although you may have picked up a much better interest rate since you purchased this truck new.