Probably an increase in fuel consumption. We went around this boat too, took the SO's old Corsa to around 5 different dealers/workshops as well as some specialist that used to tune the Super Bosses for the racing team(apparently some of the dealers thought this meant he was a car god), the eventual solution was to get rid of the car. Nobody seemed to know. Replaced injectors, cleaned this and that, would send it to be tested, the emissions were above expected, they would resolve this by making adjustments, and then car would be back 2 weeks later with high emissions (car running rich). Were eventually getting around 300km on a good tank.