The burning oil will give you the high HC readings.
Try Castrol "10W-40 Deisel" (it's a bit better than thier 20W-50), and hope that slows it down a bit.
The CO is "usually" the cat worn out. (I think).

Is the "new" carb still a Mikuni, or did they go with a Weber/Etc ?

Don `87 Mitsu 2dr, Rubicon survivor, GModified.