SULEV
BMW introduced a super ultra low emission vehicle (SULEV) into the select regions of the United States to meet stricter emission standards. California, New York, and Massachusetts received the SULEV E46's in 2003, and Vermont in 2004. They received a variant of the M54 engine, the BMW M56. The M56 meets SULEV standards, as well as partial zero emission vehicle (PZEV) and zero evaporative emissions requirements. The M56 is claimed to have identical power as its M54 counterpart.
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Information sticker on the SULEV radiator
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Engine bay of a 2004 325i SULEV
Read more about this topic: BMW 3 Series (E46)