It's no longer a rumor, In Ford's website it stated that a 2.3 ecoboost will be used. well, it may sounds stupid but I think it will do pretty good. lighter, little bit more gas saving. I kind of like the idea tho.I don't know if the rumors are true but a turbo 4 cyl engine on a mustang sounds straight out stupid. "hey what are you running under the hood of that nice new mustang?" "A tiny turbo charged 4 cyl engine." See how stupid that sounds? Mustang= Giant naturally aspirated motor making giant power.