OP was looking for more mileage and smoother performance.

Schmoozer, aren't fuel maps a PITA? I'm still working on mine for my mustang. Idle and WOT are easy...it's all the in between **** that is a PITA. Almost makes me want to put my carb back on and be done with it.

 

Yeah but lucky for me it was from a class and the majority of the data was given.

 

Unless you are racing your XJ or towing a heavy load, WOT performance is not something you are using everyday. Do the prudent thing, like making sure you are tuned up and well maintained and you will get the best overall performance from what your XJ was designed to do.