Re: custom tune........
If it's a 5.7 he has the 545 RFE....He needs a 4x4 dyno with both rollers linked.
Anything else and the Jeep will flip out and go into limp mode as it will see that the front wheels are not turning the same as the rear via the speed sensors and it will try to fix it by applying the brakes on the rear and transferring power via the ELSD's and the clutch in the T case. When it can't succeed in equalizing the power/wheel spin it will limp.
Forged, Stroked, Blown, Bottle Fed & More