Diesel Bombers - New owner needs help!!!

Hey guys. New to the site and have a few questions. I have bought a 2007 3/4 ton with the 6.7 cummins. I use the truck for pulling a camper and light utility pulling on the farm. I want to add some power to it and hopefully gain some mpg. It has 49,000 miles and I really don't want to do anything to void the warranty. Also how should this truck be driven for normal everyday driving? Is there any key points maybe I don't know about? My mpg usually is 14.2-15.3 that is city and highway 50-50 or so. I drive about 25 miles on highway one way a day. Any help would be greatly appreciated.