My mate once put these up his exhaust when haveing his M.O.T and it passed beleave it or not lol maybe you could try the same thing? just put them in the back box when you get to the M.O.T garage dont drive with then in and dont shot to much up the exhaust so that the engine cant breath! http://www.cleaningproductshop.co.uk/LeifheitStainlessSteelOvenScrubber.htm