2005 6MT UK-spec... Are the Cats in our cars different from US-specs or Japan-spec Cats? I understand that the UK-spec Cat has part number N3H8-20-55X (or something close to that) but this is different from the US-spec cars. Are the cats interchangeble and will a US-spec cat pass a UK MOT and vice versa? Does anyone know where I can get a cheap brand new factory Cat OR low mileage used factory Cat? Are there other companies that manufacture replacement Cats for the rx8 that will meet MOT emissions/Smog test?