Way more room in the front; adults fully comfortable in the back seats.
Improved gas mileage.
Gearing change for 6MT; 6MT is essentially 5MT with a 6th gear overdrive.
Bigger fuel tank for extended range.
Improved cylinder head cooling; piston shape changed for weight reduction (2.5i).
130A alternator (110A 4th gen).
Greater turning radius.
GT only 2010-2012. 47 lbs greater weight. Increased HP (265 vice 243). Stage I 5th gen = Stage II 4th gen for performance with added torque in the low end.
GT is dual AVCS.
Heads modified for better combustion; piston shape modified.
Oil flow rate increased.
No up pipe; turbo mounted on the headers.
Limited 3rd part options for aftermarket.