I just ordered one and it's on it's way. I already have a K&N intake installed and a powerraid throttle body spacer. I recorded two highway mpg averages and two around town using both what my dash computer says and actually calculating it by hand. Here's what I got:
town: actual 19.77 vs. computer 20.3
18.74 vs. 19.6
highway going to and from vegas: act:22.3 vs. 23.4 and 21.6 vs.23.2
And not resetting my computer for a month I got 20.8 mpg.
So I'll install it and let you know how it works out.

 

What was the kit number of the Fitch you installed? Was it F3824 or F3624?

 

ok im reading on their site and they state that this device apparently raises the octane rating of the fuel...since the jeep is designed to run on 87 octane any higher octane rating increases the auto-ignition resistance of the fuel. This brings up the question of is it ok to use higher octane fuels in the jeep which is not advised becasue the compression ratio of the jeep is not as high as say a performance vehicle which needs the higher octane to prevent predetonation.

The site doesnt really provide the details of how the system really works...questionable at best

The old idea that if this really does work then the auto manufactures would have put it in the vehicle already