Yes, my B7 is a 1,9 tdi. There is one B6 1,9 tdi with the button in my family, too, so I guess it is possible to have one in diesel-cars, as well. Please check this out: Fuel tank vent modification mk3 VW and Audi TDI | VW TDI forum, Audi, Porsche, and Chevy Cruze diesel forum.