I understand leaking fuel injector seals can also generate a diesel exhaust smell. Listen out for a "chuffing" sound when idling - ie air escaping from one or more fuel injector seals. At 220,000km, you might be in the zone for injector seals to fail - I had 3 fail between 230,000km and 245,000km - and have now replaced all 6 as a precaution.
