Volkswagens economical diesel-powered Jetta TDI and new GT models made their U.S. debut. In May, two late-arriving specialty models were also released--the Golf Trek and Jetta Trek--both equipped to appeal to young Gen-Xers and others caught up in the mountain-bike craze. The TDI features VWs 90-horsepower, 1.9-liter direct injection diesel, mated to a 5-speed manual transmission. The combo produces eye-popping fuel economy of 40 mpg in the city and 49 mpg on the highway. The new Jetta GT includes many of the sporty touches of the top-line GLX, such as alloy wheels, rear spoiler, and fog lamps. The interesting new Trek models start out as GL models and add the following: roof-mounted bicycle rack, Trek mountain bicycle, special cloth seats, leather-wrapped steering wheel and shifter, sport instrument gauges, delay-off interior lights (Jetta) floormats, cargo net, roof-mounted whip antenna, dark-tinted taillight lenses, foglights, and alloy wheels.