hi, thanks Ben for this post. i recently took my car into hi q in wolverhampton to align the front wheels. the guy said that the air box was leaking, and that it was full of soot and needed cleaning out. he said it might cost £70, so i decided to do it myself, and bought a mini socket set from halfords for £10. i took the cover off and removed the air restrictors as described above. my lupo was made in 2000, and i suspect that this was the first time the cover had been opened since then. there was black gunge everywhere, especially in the restrictors. even after they were removed, the air intake chambers were thick with gunge. i scraped out as much gunge as i could with a screwdriver. some of it fell back into the chambers, as they point down at a steep angle. when i replaced the cover, the engine wouldn't start. the next day, i had to get towed to a garage, where they discovered that the engine had seized due to gunge falling into the engine. they had to take the engine apart and decarbonize it, machining the engine head and the valves, and sending the injectors away to be cleaned. all in all it cost £630, at an independent garage. i just post this to warn sdi owners of the dangers of cleaning the air intakes. i thought that diesel engines were pretty robust, but it seems they can't handle a small amount of gunge falling into the air intakes. i'm seriously considering getting a petrol engine next time, as i suspect they don't have the same issues. please advise if you have any related experiences. james