Did a search on Cherokee Forum for "Programmer" and didn't come up with any real facts. Any help would be appreciated.....2000 XJ 4.0

 

superchips makes one it plugs in to your diagnostic port to reprogram the ecu it also locks itself to one vin number if you want to use it on another you have to reprogram you ecu back to factory specs google superchips to find it

 

from what ive heard they are a waste of money if you want more power get a cold air intake exhaust bore out your throttkle body get bigger injectors or do a stroker

 

Check out this tread: https://www.cherokeeforum.com/f2/performace-chip-actually-resistor-14985/ , it may be as simple as a quick trip to radio shack to buy a switch, wire, and a resistor. Then you can just have a switch to go between normal and performance.