In your opinion what are/is the best modification(s) that I could do to improve power and the mpg of my 4 door?

I've considered CAI. Is one better than the others?, and a cat back exhaust and maybe even a JET performance chip.

Currently have only replaced the wheels with 15 X 8 mickey thompson's and 33 X 12.50 procomp mudterrain tires. New bumpers are planned as well as rock rails.

 

More power....swap in a Hemi

More mpg....sell JK, buy Prius

No, seriously though. I'm trying to achieve the same and have heard mixed reviews on CAIs, throttle body spacers, exhausts, chips, etc. I've only seen a couple of threads where people have had their jeep dyno'd after each mod. Then I've heard people say the same mods were worthless. After all the searching, I think I concluded that I just have to see for myself.

 

Select the tire size you plan run and stay with. Re-gear your differentials according to the tire size selected. CAI, chips and cat-backs do add a little power, but they can never recover from the added parasitic drag and weight created by the larger tires, lift and the additional aftermarket components.


MPG........Its a Jeep, we are not in the fuel efficient category by design.

 

I have a 4dr Sahara which is my daily driver. On the stock wheel and tires (32"), I averaged 17 mpg (mostly highway driving). When I upgraded to 33" tires (same stock wheel), my mpg dropped to 14.5 - 15 mpg (all hand calculated not using the Jeep computer). After adding a CAI, Jet Chip I and catback exhaust I now average 16 mpg (again mostly highway driving averaging 70mph w/ pockets of traffic here and there). So for me all three mods helped in improving my gas mileage.