I've used the Hypertech Powerprogramer III on my mostly stock 4.0L and it did nothing that I noticed except make it ping. I know someone else that used it that had the same experience. Dino has used the Jet chip and he noticed a bit more power. No programer will change the shift points on the XJ.
I currently have a PCM reprogram from
[email protected] that does a bunch of stuff. Such as:
-removes torque management resulting in firmer shifts
-decreased the e-fan's activation temperature
-Increased speed limited from 114 mph to 254 mph (a bit optimistic there)
-Pushed the rev limiter from 5300 to 6000 RPM (useless on an auto)
-Increased the idle from 648 to 700 rpm (useful for after market cams)
-Turned stall torque off (don't know what the heck that is)
-Adjusted fuel map (applicable to a stroker with or with out larger injectors)
-Turned the cylinder misfire MIL illumination off
-Ac compressor kicks off for 10 seconds at WOT (didn't even know they could program that, but neat)
-Set cruise control range 30mph-130mph
I like the mod, but nothing in it is applicable to better fuel economy. The best thing you can do for fuel economy is a complete tune up and change all fluids to synthetics (not the transmission fluid though, the AW4 doesn't like synthetic)
