Hyundai iLoad 2009: Turbo actuator fault

I purchased a 2009 Hyundai iLoad van from my son in January. Having borrowed the van on a number of occasions I was very impressed with the power and fuel economy, but when I got it from my son it was gutless, slow and the fuel economy was poor. The dealer told me the turbo actuator was faulty and they fitted a new one under warranty in April. Four months and 9000 km later it has again lost power. The warranty expired in July. Is the dealer required to replace the actuator under warranty again as the last repair only lasted four months?