Can anyone suggest how to deal with this. Recently very smokey from exhaust even when not flooring it. A blast down the motorway used to help clear things out but this is now all the time. Any sort of tap on the throttle and I get a puff of smoke which is shown up clearly in light from cars behind at nights and also visible day time. Ive tried different garages for diesel to no avail. Clean car but dirty exhaust most annoying. Help and input would be greatly appreciated.