DETROIT (WKZO) -- Drivers seem to be holding back on buying plug-in electric hybrid cars so far this year.  General Motors, Toyota, and Nissan are all reporting a sales slump for electric vehicles and plug-in hybrids for January compared to December.  While GM reports selling more than eleven-hundred of its Chevy Volts in January, that's off from the more than 26-hundred sold in December and the lowest number sold in a single month since February of last year.