3 door, 2wd(sapph) or 4wd sapph, or escos ?
Either way I would start by changing the CTS if it over say 3 years old, as this is the main influenece of co, but also need to check others if that doesn't cure it such as map sensor, lambda(if fitted), fuel pressure etc.
It is a must that you open the ecu and see what the chip is, and more to the point that it is correct for the bits you have fitted, they all need to work together.
tabetha