Have been driving across country for about 2k miles. without fail, there is a faint, plastic intermittent rattle sound when reaching 70 mph. seems like there is air flow going to a place under the hood and dash, that causes a loose small part impinge against a plastic housing of some kind. i don't know, just guessing. new car, so it's disappointing. otherwise the car is great, I love it. Anyone have similar sound?