That FAQ is a bit misleading in that a 4.0L throttle body doesn't somehow magically force more air into the 2.5L engine since the 2.5L isn't starving for air in the first place. The 2.5L engine is only starving for more displacement.
Last year some time, Jp Magazine did a test with a 4.0L TB on a 2.5L TJ engine and the article said, if any thing, that they noticed a slight loss of performance.
Don't waste your time or $$$ on installing a 4.0L throttle body on your 2.5L engine. The only gains some will notice are from the placebo effect.