My wife had a Honda Accord V6 with cylinder deactivation. Depending on engine load, the car would run on 6 cyl, 4 cyl or 3 cyl. There was in indicator on the dash that would light up (ECO) when the car was running on less that 6 cylinders. During that time, I could feel a slight vibration. When the car would go back to 6 cylinder mode (going uphill, passing, etc) the vibration disappeared.
I have a 5.3 with Dynamic Fuel Management (DFM) and the 10 speed transmission. Although the truck doesn't indicate when the engine is operating in less than 8 Cylinders, I can feel it when is is doing it just as I could in that Accord. If I roll into the throttle, the vibration disappears completely....Again, just as it did in the Accord.