Hello. First time posting and looking for some advice please. Had our Ideal boiler serviced. The engineer said the co & co2 readings were high and that it needed a new burner seal and a strip down service. So burner seal replaced and strip down service was done. It indeed brought the readings way down. However, since the work was done the boiler is now making a loud noise when igniting and sometimes comes up with F2 error. Quick googling reveals delayed ignition? This never happened before the service and part replacement. Is there something the engineer could have done to cause this? Wanted to get some advice before calling them out again or indeed avoiding them and calling someone different. Thanking you in anticipation.