I put a 2" leveling kit from StreetRays on my '16 custom and I love it so far. It has been about 2 weeks since I installed it, but so far the MPG difference is less tha 1 MPG, and I like the look a ton better. 3 reasons I chose this kit were 1. that it was from a company that is 45 min from my house, 2. Made from solid Aluminum, and 3. the price is half of RC.
I measured before and after at the top of the front wheel well and it was a 2" gain on the dot.
link, before and after below.
http://www.ebay.com/itm/SR-CHEVY-GMC-SILVERADO-SIERRA-07-16-FRONT-2-LIFT-LEVELING-KIT-LOWER-MOUNT-/272051329039?fits=Model%3ASilverado+1500&hash=item3f5785d80f:g:T3QAAOSw--1WqANr&vxp=mtr