I just saw this thread for the first time today, so this may not help the original poster, but... I had the same problem and resolved it by accident late last year when I added a Helmet Super-Visor to my Arai Profile face shield. I was trying to get relief from the low angle October sun (and did) but was also amazed that it got rid of the noise/buffeting problem I had on my 07 GT. I can now ride with the windshield in any position without noise or buffeting whereas previously I always had to keep the windshield at it's lowest setting to get reasonably clean air. For about $20, it has solved the problem and made the bike much more enjoyable. As a side note, I found that the noise was reduced on my other bikes as well, even though I hadn't thought it to be a problem on those bikes. For reference, I am 6'1" and have a 34" inseam.

I don't know anything else about the company, but it seems like a good product at a fair price.
http://www.super-visor.com/