yes mate its on the edis modle plug i belive.

the co2 adjuster is that yes mate, it can make a difference to the running of the whole engine through driving, not a great deal but a bit, i remember when i went fot a rolling road many years back and they said my fuel pump was fcuked and it was running lean, he adjusted the co2 adjuster a bit and it ran a bit better on the way back, course i fitted a new pump and it was like a new car
but tbh, dont adjust it your self, although i guess with a gas tester hanging out the exhaust it might be possible but i tend to leave that sort of thing to the pros, its not worth me doing damage or something.