Maybe if you replace the factory Y pipe and some shorty headers combined with a CAI it may gain you 1 or 2 MPG. Once i lowerd my 11 with 24's i just changed the factory y and added a flowmaster 10 series i saw a gain from 17 to 19.5. Even on my last trip to houston i avg 20.8 running 75 to 85 mph.
2800 stall, moes ported throttle body, vararam intake, ARH LT, Flowmaster 10 series, Hemifever tune.
Best 1/4 mile: 14.30 @91 mph soon to be 13's