There is always this radiator kit sold by EAGLE DAY. It goes in the center behind the front bumper also as an add-on.
http://eagleday.stores.yahoo.net/bope.html
This radiator kit is stock for the GT3R race car and will bolt directly to the street car. Kit includes radiator, hoses, brackets, rubber grommets, air duct to match your bumper (stock, aero, or GT3R) and all necessary hardware. Professional installation recommended.
The water-cooled modern Porsches have the radiator split into two sections, one in front of each front wheel. On certain models that require additional cooling, a third radiator is located in the center of the front bumper. In particular, a 986 Boxster equipped with the Tiptronic automatic transmission, a 986 Boxster S, and a 996 911, have center radiators. However, the 986 Boxster with manual transmission and 987 Boxster and Boxster S do not have a center radiator. But the space for the center radiator is available behind the bumper, and the mounting points are there, too.