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There's only one intake on a stock ISF, but it's dual stage. A trap door located in front of the filter element opens at higher RPMs. The Injen and K&N intakes don't have a dual stage filter. They both remove all the hardware associated it. The Takeda utilizes the front part of the filter assembly and uses the dual stage feature. The JoeZ which is a tube that replace the factory tube and resonator also keeps the dual stage feature.