The 5.3 engine in my Z71 hesitates and feels as though it has a miss when driving in most conditions. On flat level ground at 55mph I can watch the Tach bounce every time it misses. I have repeatedly talked with my service department about the issue. I have been told that Chevrolet has leaned out the fuel delivery system excessively, in order to meet Federal fuel efficiency guidelines, and that it is having an effect on drivability. When I asked the dealership about adding a programmer that would allow adjusting this fuel flow issue, I was told it would void my warranty, and I would have to live with the problem.