The device does what it says. It disables the AFM and takes away the hesitation and the sluggishness. I used to have a 2005 NBS Tahoe and I regretted exchanging it for a 2013 NNBS Tahoe due to the sluggishness caused by the AFM. Now I am enjoying the newer truck due to more responsive throttle. I did notice a loss of 0.5 MPG but it's worth it for the truck to not feel like a big slug.
I was tired of using manual M5 to disable V4 mode every time I got in my truck. This Range devise does a excellent job of disabling V4 mode. I don't care about mileage because if I did I wouldn't have bought such a large vehicle but I have not noticed any difference so far because the truck has a six speed transmission. I could feel the V4 mode going in and out all the time and the vibration that happens because of it. This is a great product and I got for a great price on Auto Anything.