I drove from ATL to Charlotte back in May and averaged just under 26 mpg with my 3.73, BAMA 87 Street tune, and Airaid CAI at around 78 mph.
That excited me because I used to get far lower mpgs. She has just under 15k miles on her, and I just cleaned the filter right before I made that run; so, I don't know if she is just broken in better or what.
2011 Mustang 3.7L, 6A, MCA Pkg, Ingot Silver w/ Stone
Perf Mods: FRPP 3.73 Gears, 87 Octane Performance Tune from BAMA, Airaid CAI, Magnaflow Comp Axle-backs
Ext Mods: Lower chrome billet grille, Tint
Upcoming Mods: Lowering springs