General Motors is increasing incentives by as much as $US1,000 from Monday as the vehicle maker looks to sell down its bulging supply of remaining 2003 cars and trucks, the Detroit News reported. The paper said GM is adding a $1,000 coupon for customers who buy a model from the same branded vehicle they are trading in. For those who trade in a GM vehicle but buy a model from another of the automaker's brands, the loyalty bonus is $750.