Jim,
if i'm not mistaken, the 3.7 in the liberty is a 6 cyl version of the 4.7 that has been bored out slightly. i've driven a KJ 4x4 before, that engine , unlike the 4.7, has no balls whatsoever.
I went to home-depot and bought 3 inch tubing (1 90 degree bend, a piece of straight pipe, 1 45 degree bend) and 1 coupler. the filter i used was a 11" UNI foam filter. is it overkill? possibly, but from my experience with dirtbikes and quads, UNI foam filters filter better than the K&N and still flow very well. since i offroad, i needed a filter that wouldn't let dirt and dust get through, and i've used UNIs on all of my quads and my old dirtbike and never came across a problem, unlike my buddies and their K&Ns. the 8" filter that UNI offers would probably be good for you.
you will be amazed how much deeper and louder acceleration is after adding the intake. before my 4.7 sounded very whirry and whiny - very japanese sounding, now with the intake it has a very hemi-esque roar at WOT.
while that will free up a few ponies, what the real restriction is on the Jeep 3.7 (hell, all jeeps really) is the exhaust. do a carsound (magnaflow) hi-flow cat and a magnaflow cat-back. pricey, i know, but -no joke- with the intake and exhaust you will unleash like 30 hp/35 tq.
you can thank me later
