Have you tried going to a dealership and seeing if they can check it out? Maybe resetting the adaptive learning, or something along those lines?
Seems odd you're not hitting your EPA estimates, this is the first car that I've been able to beat them regularly. All my domestics would be lucky to touch the EPA numbers even on a flat freeway with CC on.
2013 BMW 750i - Coded, Executive, Lighting, Cold Weather, M Sport, M 303 Wheels, 5% Tint, Conti DWS Tires, 3M Bra, Front DE Plate.