My steering in my Sportivo 2005 made a really loud noise just last week, similar to the sound/whistle produced if you were blowing air over the top of an empty glass bottle, except much amplified; this was when I was reversing out of a parking spot at a shopping center. The noise went away after a few seconds. It hasn't made any other strange noises since, and I don't recall such a loud noise over the 1.5 years I've owned this car. My previous car was a Holden VH 1982, that had a horrible power steering fluid leak, and a loose belt, so I know quite well what sounds are produced by both those conditions, but this sound was nothing like either. It doesn't sound like the same problem you're having though, I'm guessing yours is frequent. My last service was 5 months ago, and my car has only done about 45,000k's. Should I be concerned?