On a Jeep 4.0 the performance gains are pretty minimal because the computer isn't really aware of the increased air flow due to the lack of a MAF (Mass Air Flow) sensor. All the Jeep engine can really see is throttle position, intake temperature (which it is very sensitive to) and vacuum/boost. The computer is tuned to stock parameters, so new stock performance ultimately is about the best you can expect to get w/o modifying the computer, or adding boost. So, unless your stock intake is horribly restrictive you're not going to notice much.
On engines with a MAF sensor you tend to notice better gains once the computer has had a chance to adjust to the new intake and the increased air flow. Unfortunatley Jeep's don't have one.
I've done a lot of experimenting with the 4.0's and really the only thing aside from forced induction (been there, done that, won't do it again) or a stroker upgrade that works is the Edge Trail Jammer kit. The reason it works is because it remaps the computer slightly to take advantage of the increased air flow.
A simple intake or throttle body on it's own doesn't do a whole lot, but the Edge kit combined with the intake, throttle body, and computer module did make a noticeable difference on my Jeep.
FWIW I went to the Edge kit after removing the turbo I had. Initially I went to the turbo because my Jeep was a dog on road and I couldn't stand driving it. I wanted a little more power and there wasn't really anything available that could deliver enough of a power increase to make me happy. The Edge kit works great, after having removed the turbo I figured I'd hate driving my Jeep but the Edge made enough of a difference that I'm happy with it. It doesn't offer anywhere near the power increase that the turbo did, but it's definitely better than stock and it's exactly what I was looking for in the first place. I wasn't after insane power (although I did like it w/ the turbo), and I didn't want to sacrifice driveability. The Edge kit has been 100% reliable so far too, and it offers the same level of driveability as stock, something I couldn't say for the turbo.