Within the last week my Scirocco 2.0 TSI (11 plate) has intermittently been misfiring, most noticeably shortly after changing gear when accelerating. On occasions the catalytic converter warning light has appeared on the dashboard but has not been permanently displayed. It has 35,000 miles on the clock, has been driven carefully and serviced annually. Do you know what the likely cause of this is and whether it is likely to be a costly repair?