They are small fins mounted to the rear roofline to improve the aerodynamics of the car. They were proven by mitsibishi's wind tunnel tests to be effective for the 8 and 9. Their purpose is to decrease the coefficient of drag and to keep the flow attached longer which directs more flow over the wing hence increasing downforce.
Here is a technical article from Mitsibishi if you are interested in the fluid dynamics:
http://www.mitsubishi-motors.com/corporate/about_us/technology/review/e/pdf/2004/16E_03.pdf
Here is a technical article from Mitsibishi if you are interested in the fluid dynamics:
http://www.mitsubishi-motors.com/corporate/about_us/technology/review/e/pdf/2004/16E_03.pdf