its a sound modification... if you want to add the growl without reducing power take your stock intake and flip it, the center lid is removed by removing the torx screws around the edge. inside you will find a set of channels that keep the air flowing in a relatively straight path to the throttle boyd ... dremel these out and presto, you have growl ... add some k&n filters and you have some more growl. then buy some DEI thermal tape and cover the entire center lid and air boxes with it and you'll keep your air supply from becoming heat soaked in traffic (or at least make it not as bad hah)!