I will not tell anyone they are nit picking as my 2011 only has 130 miles. My 5.3l is running fine, I did notice a little shutter when idling after delivery. Remember your truck has a VVT motor. Gas quality and octane will effect it's performance. My last truck had VVT and the difference between when my wife filled it from near E to full with 87 to my usual fill of 93 was very noticeable. With a non variable cam shaft octane increase has near no effect unless timing and other inputs are adjusted manually. I have also noticed with my time as a tech in the military; A computer controlled trans and motors learn inputs from a driving style and use those regular inputs to tailor your vehicles performance. Example, the first Gen up armor Hummer, had an new updated brain that not only controlled the trans up and down shift set points, it all so controlled fuel/throttle. When a new driver would jump in and have a drastically different driving style, the dam thing would go into "safe" mode. An operator was stuck in no higher than 2nd gear while the truck computer was "protecting it's self". We would get a recovery call, tell the operator to park it reach behind the driver seat and hit the reset button. Being a GMAC design this was the first real world application with the Allison trans. So, if your driving style is more often to cruse the vehicle it will adopt that as the desired setting, thus drop into V4 and as your finding. It's just not meant for the sudden bursts of low end grunt, especially if your running low octane fuel. Now your fighting driving style and the VVT. My self, I'm a lead foot and that is how I'm breaking in my vehicle. I have since filling with 93 and jiving a nice short skinny pedal jab have noticed the truck is jumping to a low gear as soon as I'm near full stop. They do learn, ask if the dealer can wipe the memory, or start running higher grade gas if you want better performance. Another consideration is where you are buying your gas from; We have what we call "res gas" up here in Buffalo, NY. While it's cheap on the reservation, the quality is bad and contains lots of water and lots of water absorbing chemicals. As a Ford dealer tech years ago, I have personally removed fuel filters with what looked like tooth paste in it. It's not just the "res" either. Some station tanks either leak ground water in them or are older poorly insulated, condensation and poor maintenance lead to bad quality gas. If you think weights and measures keeps a close eye one quality, your mistaken. Some stations in my area have had three and four owner changes over the thirty seven years I've been in Buffalo. Guess how many have serviced their holding tanks, guess which ones I don't fill my truck at. I am in no way convinced that GM dose not still need to tweak this system, and that it's all or none of the above, it could be a combination of many factors. Good luck and good hunting, no for an answer is not an answer. Hound your dealer and GM till you get what you paid for. If this problem becomes more and more a pain for them and enough people bitch, the fixes follow.