French carmaker PSA Peugeot Citroen has unveiled a filter which it said virtually eliminates emissions of noxious particulates, tackling a big handicap in diesel motors in which it is a world leader.The Chairman, Mr. Jean-martin Folz, said the patented filter systems cuts down particulates to the level emitted by conventional engines, or "almost zero" complying with European norms set for the year 2005.