[Christ]

Frank - you're working with a wholly different beast!

IMHO, some carb tuning would benefit you greatly in that F150 of yours (I'm guessing it's an older truck, possibly with a 300 I6? Most of the I6's power is in the lower end. It's capable of revving up to make even more power, but requires extensive work to do so reliably.

Most of the sluggishness in the 300 is in the restrictive intake and exhaust design. Not to mention the intake is heated by the exhaust manifold, since they bolt on the same side of the head, and interlace each other.

Solving a few of those problems will probably get you on the way to much better fuel mileage, I'd say.