Is it worse in cold weather? We have the 'whine' on ours, very similar to what you've described here - i.e. it's not there just as the steering comes back to centre, but comes on after a few seconds, then is there if you turn the wheel to about 13:00. Garage thought they'd cured it, but we've had a bit of a cold snap today and it's back! Given that the oil will be thicker in the cold weather sounds like it might be the gauze issue that we are having too.