S24, E2: Matt LeBlanc and Chris Harris embark on an all-season US road trip in the latest convertible supercars from Lamborghini and Porsche, journeying from broiling desert to snowy mountain. Back at the test track, Rory Reid sets the toughest of driving challenges for Chris and the Alfa Romeo Giulia, while actor David Tennant takes a spin in the new Reasonably Fast Car.