EMDX 70, one of the original SD70ACe demonstrators, was spotted back in Denver, CO, by numerous people over the weekend of 21-22 Apr 2007. The unit has been modified, and is headed to the Transportation Test Center east of Pueblo, CO. There's no official word on what the modifications do, but the railfan rumor mill suspects that they're an air-air heat exchanger involved with meeting EPA Teir III emissions standards.