Not all passenger vehicles are created equal when it comes to the amount of pollution that flows from their tailpipes. Minivans, sport utility vehicles and light duty pickup trucks all throw off higher levels of nitrogen oxides and other smog causing gases than cars do. This happens because they are not subject to the same emissions standards that ordinary cars are. California wisely did away with this inequality on Nov.5, issuing new, more stringent emission limits that will also apply to minivans, S.U.V.'s and light duty trucks of up to 8,500 pounds, starting with the 2004 model year.