I gather that dumb plastic around the wheel wells and cheezy ebay LEDs around the headlights makes the 2014 Sierra more "Professional Grade".
I saw the Mythbusters one. I wonder if a bed cover helps to improve gas mileage at all, on the race trucks used in the NASCAR Camping World Series they sheet metal over the back of them.
Would have been interesting if they tried that in the wind tunnel as well.
As someone else mentioned, I would bet that would depend on the cover and existing truck characteristics in the tunnel...if the wind already passes over the bed without turbulence, then adding a cover might be a wasted effort; a loose toneau flapping in the wind (my dad's truck comes to mind) might actually cause drag where as a hard toneau might not have as much drag, but weigh nearly 100 pounds (added weight negates fuel savings).
Grrrrr, the OP in this thread is from TruckingTimes ... and Google Chrome flagged the entire Chevy Truck Talk forum because of the content in the ONE POST that was copied from that other website.