I believe the difference is pistons, cams, turbo. Mustang has different cams and the turbo is the big difference.I'd be curious to know what is different other than tuning. Do they have different cams? Different pistons/rods (material, cast vs. forged, compression ratio, etc)? Intake manifold runners designed with torque in mind? There is plenty of information about how the Rangers 2.3 is based off the Focus RS motor specifically and what parts they share.