I like the Superchips Flashpaq for the 3.8L. Can't speak for the 3.6l. We have 3 Jeeps and 2 trucks all with Superchips. The tunes do make a difference.
2008 Black and Khaki Sahara Unlimited. Auto, Tow pkg, Dual Tops, MyGig, Trax-Lok rear diff. 3.5" Rock Krawler fr springs, rear TeraFlex 2.5 BB, 35x12.50x17 Pitbull Rockers on Blackrock Viper Alloys, Flex-o-lite trans cooler, Mr Grille billet grille inserts, AEV Prem Bumper ETC.. AND a Locked and Lifted Honda Foreman for when the trails get real tight