There are two guises of the L8, early ones were known as 'red tops'these use the mixture adjustment, whereas later 'green tops' have CL, which you need as you have a cat, unless it's been removed, these use CL for mixture adjustment.

You really need to get the CO checked, although there is a 'global reset', I can't see how you can ever do this without monitoring the emissions, expecially with remaps etc, it sounds like this may be too lean, it's also very dangerous to mess with this as it subtracts a percentage from the fuel map, so it can end up with it running lean!

Martin