alone... i can attest that you wont see crap out of a throttle body alone. though mine isnt extreme as the 5.0 swap, isnt that like 70mm? i could be mistaken, probably am. the only way to see significant improvement is to add a more free flowing head, more free flowing exhaust, intake, and play with WOT air/fuel mixtures all together... all that for a 4.0? not worth it. put that $1k else where.
if you want gas milage from a lifted jeep... gears. or get a honda.