I've got a 5.4 in my '06 F250 and bought my "new to me" truck specifically for this engine equipped with a 6 spd manual transmission. I previously owned a 1/2 ton Chevy ext cab with a 5.3 and an automatic. The 5.3 is listed with lower HP and torque numbers than the 5.4 but it felt a lot more responsive on the highway. My 5.4 is feels like it has quite a bit more power down low, but also feels like it goes flat at highway speeds. I don't have any problems making passes on the highway, but the engine just doesn't feel very impressive compared to the 5.3.

Could this be a case of auto versus manual trans? I know my 5.3 felt weak on the bottom end when towing my big enclosed trailer so I'm thinking my old Chevy was a lot more of a commuter/highway truck than a work truck. In any case, the contractors I work with all have the opinion that the 5.4 is a gutless wonder, especially when it's hooked to an auto. One of our work trucks is an Expedition with a 5.4 and it does not feel as strong at highway speeds as my 5.3 did. Why does the 5.4 not feel very impressive?