The company said it’s the fastest Vespa in its American lineup. The GTS 300 Super is the bigger brother of the company’s GTS 250, with a slightly larger engine and some racier styling. Paolo Timoni, the chief executive of Piaggio Group Americas, said he expected Vespa’s American sales to improve in 2009, even after a year of substantial growth in the United States. Through the first three quarters of 2008, American sales of Piaggio’s scooters (which include Vespas as well as Piaggio-branded models) were up 61 percent, Mr. Timoni said. The GTS 300 Super will go on sale in March at a suggested price of $6,199.