Is anyones car doin the same thing? My car makes a metal type of hissing noise. The more I give it gas the louder it gets but on the highway i cant hear it. Its not the supercharger cuz that makes a whirring noise. This noise sounds almost like a exhaust leak or something. I have read an article about this car and the driver mentioned something about a noise like the one im talking about. I drove another c230k and it didnt make this noise but the one i drove was a 1.8 liter. If that makes a difference.