lol... (If I can say that here)
OP, once you pull off your existing exhaust manifolds (which will be HARD), you'll see the majority of why we call it the 3.slow. One tube almost blows right back up the other. In the 2001 cat I have, Downey claims their header will do 11hp when routed back to the stock exhaust. 14 and "radical bottom end" when routed through their 2 1/2 system...
If I had the money, I'da done it LONG ago... I have a 14mm head bolt 3.0 and it's NEVER let me down... I love the things... well, except for the bad MPG's it gets, but I've got a intake gasket leaking...
As for the Cold Air kit, most are just tubes that get the intake inlet out of the hot engine compartment. And most run low to get it. In a 4wd that defeats a lot of purpose and it's kinda a waste of time, unless it never sees any water or mud.
You can get cool air from a cowl induction to, but that's either a custom piece, and or gonna get expensive. My guess as to why it's not done a lot is b/c of aerodynamics...
A Safari or ARB Snorkel will work to.