my 2cents:
I've seen little hard evidence that either the Gotts mod, a CAI or efans, pulleys, etc. make any significant difference. lots of stories, but no actual numbers.
These may be helpful as part of a completely integrated design, but I would not waste time with stand alone aftermarket add-ons.
Opening up the breathing, in and out, when properly done, should be helpful - remember your motor is just an air pump, after all. But, keep in mind, opening up the breathing will also pass more gas through it. it's next to impossible, and certainly not cheap, to get significant power and mileage gains at the same time.
Ford's done a pretty good job with the stock suspension. I'm not aware of any aftermarket component that will improve on it significantly without altering ride height. You can get better durability out of it, though.
It sounds like what you might be looking for is a long travel suspension. That would definitely improve suspension performance off road, but it would not be cheap - I'm not aware of any available kits in the aftermarket for the late model expedition. Doesn't mean it's impossible - there are some mechanical geniuses out there capable of simply building it from scratch, but they're not cheap.
circling back around, I've been looking for hard numbers for CAI, efans, etc. for a couple of years now. if anyone has done before and after dyno runs, I'd love to see them. I can't even get anyone to produce before and after intake temps for a CAI.
I do not care for the manufacturer's dyno runs in a pristine lab environment on an engine stand. The theory is correct, so it would be odd if they could not generate good numbers. But, it's the actual application on a specific truck that has yet to produce real worthwhile numbers.
I started this process (on my last few trucks) intending to do all of the above. Gotts, CAI, efans, pulleys, etc. I did the Gotts mod on an F150. the results were so disappointing I started to look past the anecdotes and obvious ********, looking for hard numbers. that was several years ago; I have yet to see real-world numbers worth the money.