Hope this is not to late to add to this part of the forum, but I would like to give my 2 cents in a Mod I did to my jeep about 1 week ago. I had my jeep running pretty good and fast with my existing mods with cold air intake, bored out 2.5L TB, TB spacer, accel coil and wires, NGK plugs gapped at .037, catback with magnaflow muffler, she was moving pretty fast. Then I finally did the 4.0L throttle body swap. Just the factory 4.0L TB not bored. I know some swap to bored TB like 62mm. But anyway just with the factory one I must say WOW what a difference in off the line response, Its like instant. She climbs up to 80 MPH with no problem. On a head wind and uphill she holds her speed at about 65mph. And to top it off I am saving gas, due to not having to push to far down on the pedal. My jeep feels a whole lot better, It feels like a nite and day difference. I highly recomend this swap.