They check emmisions on a federal level. Before they can produce a car in the US, every engine "family" has to pass a series of emission test. If that engine does not pass then the manufacturer is fined for every engine that is put into production(gas guzzler tax). Since no one is going to pay that for a 240sx they said screw it and put the KA in it. (more emissions in US than europe and Japan) Thank CARB.......