One of the most important launches for General Motors Co. and Chevrolet this year isn’t necessarily a vehicle, according to Chevrolet Chief Marketing Officer Tim Mahoney. It’s the launch of the Detroit-based automaker’s in-vehicle OnStar 4G LTE. “This is a game changer,” he said during anAdcraft Club of Detroit meeting Wednesday in Detroit. “You talk about finding new roads, you talk about ingenuity. We will be the first and only company with this across a wide variety of our product line.”