Mother Jones: Days after Volkswagen admitted that half a million cars it sold in the U.S. contained software enabling them to evade clean air laws, top Environmental Protection Agency officials said they are planning to toughen emissions testing for all automakers. The EPA now plans to examine vehicles for so-called defeat devices. In a letter released Friday morning, the EPA said that federal regulations allow the agency to "test or require testing on any vehicle at a designated location, using driving cycles...