hi i have a 98 1.6 16v astra (x16xel) and its got a hell of a bad misfire when cruising but never happens when under load. its not the coil pack as i have tried three today but on testing i found that no.4 cyclinder wasn't sparking. the figures for the airflow meter seem to be reading fine. there is no trouble codes stored, its had new spark plugs fitted but no difference. i have some injector cleaner to try over the next couple of days. but could this now be down to the ecu?