I agree U.W. but they kinda go hand in hand. Low end is okay but there is absolutely no medium to higher end in the 4.0L at least mine which is a 5 speed.  

I drive to work on the highway so HP would help,somewhat.  

I've seen these overdrive units that mount on the back of a tranny but would they work with a transfer case too?  An old buddy of mine swears by his.  Installed it in an old IH pickup and he claims it improved his mileage by 5 mpg and kicked up his top end speed also.  

actually ibfox you are going to get better performance out of a plastic tube. the plastic takes in less heat than a aem brute force metal tube. the plastic tube is very stong unlike the metal tube which can dent easier.

to pete barton, no tj's came from the factory with a header. it is an exhaust manifold. it may look like a header because it is tubular, but the tubes arent of the same length making it an exhaust manifold

Ohjpr hit the nail on the head, other than mentioning what 96zj did the reason they didnt idle long is partly because of the cam too.

to pete barton again. it would be a good idea to reprogram to get an adjustable map sensor if doing a cam, hi flow head, or ported exhaust and or headers, or stroking the engine

to joejjeep, why would you refuse to buy a rubi? you get everything you need, its underwarantee, its installed you dont have stock parts laying around which is money laying around, it comes out to be cheaper on you and its all done without stuff to go wrong all the time. you have your axles. your 4.11s. transfer case. moab wheels. mud tires(could be better). all your electronics and switches already ran. a rubi is the way to go.

and who ever said that jeep 4.0s were fast. they are alot more torquey than the 3.7 but your right the 2.8 would be sweet. if you want more torque regear it.

just my 3 cents.
sincerely
a proud rubicon owner  

K&N has a heat wrap with there kit and they have the name to back them!!!!!!!!!!!!!!!!!!!!!
Been around alot longer then brute force.
Thereare certain things that you get what you pay for and this is one.....
I have had a K&N system on all my vehicles for years now they have never let me down...
Better quality in K&N

Nuff Said!!!!!!!!!!
P.S. Also invest in headers and a exhaust system I have Banks!!!!!!
And a Bigger throttle body.....