HI, NOT SURE IF THIS EXISTS,,BUT WITH DISCOUNT BEING TAKEN AWAY IN PARTS OF LONDON ON CONGESTION CHARGE- DOES ANYONE KNOW IF FILTERS CAN BE PUT ON 997/996 TO WITHIN THE CO2 EMMISSIONS-/ OR REDUCING THEM ETC- I THINK THE TOLERENCE IS 225 CO2 GRAMS PER KILOMETER THANKS IN ADVANCE!