My French is not great but this looks like if you buy any car over 200g/CO2/KM then there is a one off 8000 euros tax at purchase. In fact you need to be under 130g to pay no extra 'Malus' tax:
http://vosdroits.service-public.fr/...on&l=N18131&n=Mesures anti pollution&l=N19924
http://vosdroits.service-public.fr/...on&l=N18131&n=Mesures anti pollution&l=N19924