Buffeting is an aerodynamics issue with your bike's setup, and your position on the bike. It is often caused by the wind snapping around an improperly fitted windshield. There are several ways that you can reduce the effects of the wind on you.

1. Change your windshield - Either buy a windshield, or change your current windshield. It's hard to say exactly what will work before trying it, but generally if the top of the windshield is at nose-level, the wind should flow around you. Some windshields allow for adjustments so that you can experiment with what works best.

2. Buy lowers - Lowers attach to your fork or highway bars and deflect the wind away from your legs. Although you may not think that the air at your legs is the problem, wind works in funny ways. I've found that good lowers usually solve most buffeting issues.

3. Adjust your riding position - Lower your seat, lower your bike, get pullback handlebar risers, etc. Certain spots behind your windshield can be worse than others.

4. Change your helmet - As Bob mentioned, going from a halfie to a full-face can change your aerodynamics and reduce buffeting. On the other hand, going from a full-face to a halfie may change things for the better as well. Experiment.