This is something as a parts manager i hear frequently. First step would be just verify they were installed correctly. You'd be surprised both how often a dealership will put them on just an inch incorrectly, and you wouldnt believe how much of a difference that inch will make. unfortunately most cross bars suffer this fault, and aside from taking them off, theres not much that can be done.
There is an easy and simple solution for the whistling sound. On the underside of the bars on either side are the holes for expanding the bar ends to fit properly to the roof rails. These holes act like whistles when the wind is flowing over them. I covered the holes in both sides with a piece of duct tape and the whistling noise has completely stopped. Cheap, simple, and easy fix![/QUOTE]