My turbo whistles so i just live with it. When i first got my A3 the turbo whistled & everyone said its was fooked. I spent x amount on a brand new unit & x amount again on fitting. It was fitted & same noise so i know the turbo is ok. It can be sat idling & all quiet then the panpipes start. If i blip the throttle it stops again for a bit. Driving along it whistles whilst it spinning up & when cold i can hear the DV. I know the turbo is ok so i,m not worried about it.