I recently bought my first E (Nov. 7th) and had the dash noise over the "right kind" of bumps. I could duplicate it by lightly pounding on the dashboard and noticed the rattle stopped when I pushed into the corner of the dash where it meets the windshield and the A pillar. When I let go the dash would spring up a bit and the noise would come back. So, I cut a couple of square 1" x 1" pieces of pipe insulation and headed out to the garage. I pushed down on the corner of the dash again and stuffed the pipe insulation in there to keep the dash from springing up again. I put a piece of insulation in each corner and the noise went away. I stuffed it far enough in where you can barely see it. We still have bumpy icy roads and the cold weather tends to increase rattles anyway but the spongy pipe insulation material still works so far. It also blends in as it's a dark grayish/black color.