Two things...... 1) Guess I'm one of "The 44,000". The AFM in my 2011/1500LT/5.3L/3.42/4WD works perfectly. There is no perceptible change in anything as it switches mode. It appears that, in general, when the instantaneous fuel usage rises above approximately 20mpg, it switches to V4, and then switches back to V8 when the instantaneous usage falls below approximately 18mpg. Unless you are looking at the fuel usage display in the DIC, there's no way anyone in the vehicle would know what mode it is in, or when it changes mode. When it's in cruise-control at a steady speed on mainly level roads in V4, a slight press on the accelerator immediately switches it to V8 until the accelerator is backed-off. Then it switches back into V4. I routinely get 17-18mpg in typical around-town driving. It has gone as high as 21.5 in mostly-highway driving. I do not drive like an idiot. Maybe that helps. 2) For all of you having issues -- if your truck has a spec like mine (and perhaps others, I have no way to know), you very likely got new engine controller firmware pushed to your truck sometime in the last week or two. You might want to see if its behavior has changed lately. And yes, GM can push new firmware to your engine controller while it's sitting in your driveway. It does not require a visit to the dealer.