Just got done tuning an 06 LLY/LBZ, and he went from getting 18-19 running 65 with his bullydog triple dog to 21.5 now doing the same exact trip except now with an EFILIVE tune I put in it for him. I believe he said stock he was getting about 17-18. Stock tuning in teh LBZ isn't the best for milage IMHO, theres no reason to be holding 5-6 pounds of boost while running 55 with no trailer on a flat road. It does make for a responsive truck, but is hurting the milage.