Given your high CO the tire dry test probably won't help your situation, but it will help if HC is near (or just over) the limit as in my case. If the mixture is properly controlled, engine out CO before the converter should be no more than 1.0 percent. Your CO at over one percent after the converter indicates too rich a mixture.

The first thing you need to do is check the O2 sensor output and duty cycle. Even though your O2 sensor is young, it could be the problem, If its output waveform is okay, then the problem could be the basic mixture setting on the fuel meter or the EHA or somewhere in the electronics. As our cars age, connector problems are common, so removing and inspecting the ECU and EHA connectors might do the trick. Sometimes just "cycling" connector - just removing and reinstalling them - can solve problems (old trick in the computer industry), but a thorough inspection for dirt, corrosion, or bent pins/damaged receptacles is the best idea.

Duke