( http://www.TFLcar.com ) At just about a mile above sea level the new 2013 Mazda CX-5 versus 2012 Subaru Impreza are two of the most powered-challenged cars that we've driven this year. That's because these cars are designed and built with great fuel economy as the goal but when you combine their naturally aspirated engines with the lack of air in Denver, Colorado the results are predictable. So which of these two cars is the fastest. We found out the old fashioned way: a mile high drag race.