what cool air intake filter kit work on the 2008 cadillac ext, and does it really add horsepower and mpg.

 

In the old days, cars took the air from the engine compartment. Modern engines now take the air from outside the engine compartment.

YES, more hp .. the colder, the denser the air is, the more oxygen and theoretically, the more hp you get.
THAT is exactly what NOS does .. provide lots and lots of EXTRA oxygen.

But, doesnt your car already come with one factory installed?