Spoon Sports Drop In Performance Air FilterNew version features a multilayer urethane material instead of the OEM high density paper material. The use of urethane dramatically improves filter efficiency. Upon full opening of the throttle, a huge volume of air is drawn in at high speeds. Meanwhile, when the throttle is closed, an inertial force acts and air is compressed at the instant just prior to full closing. When the accelerator is subsequently depressed, the sealed cleaner box is