Boston Globe: Craig Wedge floors his pickup and the souped-up diesel engine of his Ford F-350 Power Stroke rumbles like a muscle car, blasting black smoke through an unfiltered exhaust pipe. He and other diesel enthusiasts call this burst of unburned fuel rolling coal; for many of them, it is an act of protest against environmental regulations. In defiance of the law, coal rollers disable or discard their trucks pollution controls and modify their engines to maximize power and blow smoke with the flip of a...