David I hold emission certs from Carb. in Calif and have serviced foriegn
cars including MBZ and Porsche 930 etc. for 20 years. If the co is high the
mixture is rich. period. not lean... If I was incorrect my cars would not
pass Calif rigid smog check. Yes High HC can mean a misfire which may be
caused by a lean,,,,not rich mixture....You can get high HC with a rich
mixture which would be reflected in the high CO content as well but a high CO
content only...repeat...only means a rich mixture. Ed..