The factory throttle body of the 2.5L is a paltry 52mm in diameter. By swapping to a 4.0L throttle body you bump up to 60mm for even more flow. Beware though; the opening in your factory intake plenum is only 52mm. There is no point in running a bigger throttle body without also hogging out the plenum. Also, the idle air control solenoid (IAC) housings have a locating tab. The 4.0L IAC housing is different than the 2.5L IAC housing. You need to install your 2.5L IAC housing on the bigger throttle body before bolting it on. There is a tab on the intake plenum that will interfere with the tab on the IAC housing from the 4.0L. This swap will open up an approximate 5-10hp.