US Spec M156 engine are equipped with charcoal filters installed in the upper halves of the airboxes. To make room for the charcoal filters, the mass air flow sensor housing has a restrictive profile. Non US Spec M156 airboxes, commonly nicknamed ROW Airboxes (Rest of the World) do not contain charcoal filters and are manufactured with a much higher flowing mass air flow sensor housing profile.
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Increased Horsepower
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Increased Air Flow
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Better Throttle Response
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Includes New MAF Sensors
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Set of 2
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Bolt on installation