US crude exports have boomed since the decades-old ban was lifted less than two years ago. : NEW YORK/HOUSTON, Oct 30 (Reuters) - Tankers carrying record levels of crude are leaving in droves from Texas and Louisiana ports, and more growth in the fledgling U.S. oil export market may before long test the limits of infrastructure like pipelines, dock space and ship traffic. U.S. crude exports have boomed since the decades-old ban was lifted less than two years ago, with shipments recently hitting a record of 2 million barrels a day.