Mmmmm by ear not always the best way if it's not sounds like a rattle trap it's not advanced and if there is a major un burnt diesel smell in the exhaust it's really retarded mine on The Pig was 9degrees retarded and smelt so bad in traffic I would get a head ache The joker was advanced to were it sounded like a stroker or a 4bt straight rattle trap both were set by my ear and I timed and both trucks were 1 or 2 degrees off