As said there is no reason for high emissions when running correct, First I would find out exactly the author/spec of the chip you have, to do this requires opening the ECU and if your lucky and have a good one it will be marked up with the above information. You can then contact that tuner and find out the value of CO for that chip and set accordingly, it may even be marked with it.

I would then start with a small adjustment on the CO potentiometer (The famous screw on the ECU) to see if it changes, to do this you need a exhaust gas analyzer which the MOT tester uses, it's cheaper and easier then shelling out for a CTS which may be perfectly ok!

Most important thing is remember how far you have turned it as it can be very dangerous to play with this as it alters the fuel map as a percentage hence why it is dubbed the global mod.

It is not uncommon for ill informed meddlers to play around with them over the years.

Martin