Chris,

It depends. Do you have the 4 banger or the 6? (2.5 liter or 4.0 liter) You have more factory options if it's the 4.0liter engine (a good Jeep engine, BTW). If it's the 2.5 liter, your only choice is a replacement for the OEM filter; induction system stays stock - with K&N parts. You can fabricate anything you like... as long as there are no emission controls on your factory induction system and as long as there are no specific state laws against modifications to factory induction systems on street-legal vehicles.

If you have the 4.0 liter, K&N also sells thier "FIPK" (Fuel injection performance kit, IIIRC), so you could either simply replace the OEM filter OR replace the factory induction system and OEM filter. If you use the FPIK, you'll see a small horsepower increase - maybe about 7-8 hp - but the throttle response will FEEL better (hard to accurately measure how much). It will also make more noise than the factory induction system when you put your foot in it - a surprising amount of induction noise; it's not loud, but it's very noticable and some find it annoying (doesn't bother me).

You can gain more HP at useful RPMs with your own modification to the factory setup - anybody can do it - but those are beyond the scope here - search the Jeep forums out there; I've seen lots of well-documented (pictures) how-to articles - at least on the 4.0 L engine. If you can't get an exact hit on the Wrangler, look at the Cherokee/Grand Cherokee forums - just stick to your engine and the rest is minor details.

If it were me... I would build my own induction system with snorkle, swirl section with dirt-dropout, new filter box, K&N filter, greatly improved flow to manifold, and MAYBE a spacer. And it would be water-tight enough to ford with. My snorkle opening would be different than the conventional type sold by ARB and others. But I don't have a Wrangler to tinker with - YMMV.

Anyway, the FPIK works really well - I just am not crazy about it. If you spend the $ now for a K&N filter, you can decide later to modify the induction system (or not).

HTH, but it's your money and your Wrangler.

Tom