Trent, I bought his tuner for my 5.4 You get 3 tunes with it anyway, so if you just want economy you will get two freebies. I chose economy 87, performance 87 and towing. Towing is very weird unless you are towing as it drastically changes all of your shift points. Performance is what I used solely after I messed around with each one for awhile. Economy didn't do much of anything. IIRC I got about 1 mile per gallon difference with the tuner using any of the 3 tunes, so unless you want the 'wake up' of the performance tune I don't know that I would completely recommend spending $500 for one.
If you have a V10, his tuner is said to turn it in to a real beast, but with the 5.4 not so much in my experience.
Keep in mind that if you are really wanting to spend money trying to get more fuel mileage out of a 5.4 then you should probably just buy a Civic to park beside it. If you want more power out of a 5.4 the best solution is to floor it, as they do go pretty well when you rev the hell out of them.
I doubt this is great news to hear, but it is my experience so I hope it helps.