A pair of independent Dane County car dealers have sued Volkswagen Group of America, joining the rush of plaintiffs hoping to become leaders of class actions over VW's recently exposed use of secret software to defeat admissions testing in its popular diesel vehicles. In their suit, filed in federal court in Madison, A to Z Auto Sports , of Madison, and MSI Auto Sales and Repair, of Middleton, claim they each acquired VW Jettas over the summer that contained the devices that activtivte emission controls only during emissions testing.