Hello, I have a 2015 Silverado 2500HD Duramax. When I get up to about 45 mph a whistle noise starts all the way through till about 75-80mph. It isn’t constant and will intermittently start and stop. It sound like it coming from the Roof marker lights or the top of the windshield. I took it in to the dealership. They test drove another truck off the lot like mine and they said it made the same noise. They said they tested a bunch of things but can’t figure out where to noise is originating from. The truck has regular mirrors and marker lights. Has anyone had the same problem and hopefully a fix?????????????