I have a 2012 Hyundai Santa Fe GLS 2.4L engine. I notice that the car stumbles on acceleration. Took into the dealer and could not find anything wrong with it. There is no check engine light. The car feels like it lags power, the rpms would come back down and rise up when you let go of the gas. Under load the rpms will drop. Does anyone know if this could be the bad mass air flow sensor?