The U.S. Justice Department on Monday filed a civil lawsuit against Volkswagen AG for allegedly violating the Clean Air Act by installing illegal devices to impair emission control systems in nearly 600,000 vehicles. The allegations against Volkswagen, along with its Audi and Porsche units, carry penalties that could cost the automaker billions of dollars, a senior Justice Department official said. VW could face fines in theory exceeding $90 billion - or as much as $37,500 per vehicle per violation of the law, based on the complaint. In September, government regulators initially said VW could face fines in excess of $18...