tested --hc--141---limit220---pass ------tested--co--4.59---limit1.20---failed----co2---9.13% ----------1990 740 non turbo idles,runs and has good power.ckd air filter,fuel injectors,charcoal cannister all ok. other possible causes could be catalytic converter or oxygen sensor. if converter was bad,would not my hc readings be high??? what are the reading for a good o2 sensor?????? if bad is there a universal o2 sensor or factory only o2 sensor. what are part numbers and who to order part from???? what is good price???? by the way the injection system is rex/regina....the testing people say a large number of cars that fail the co test have def. sensors.