greetings, I've been reading the posts for a while and thought I'd weigh in... I travel 500 miles/wk in my 80 240d and at certain highway speeds i could use some earplugs... just highway noise and drone from the drive train. i'll probably try some extra sound proofing but I'm loathe to use anything that absorbs water (my days spent at a new car dealer in the 70's and the smell of wet floor mats backed by felted pads). Anyway, I have had some success with the foam mats of the material used for backpacking. theyre easily cut and don't absorb moisture...no rust underneath. Also there are fiberglass wool mats used for sound deadening in office interior panels. similar material available for supended ceiling panel and then the polyester fiberfill batting at fabric stores.... just some thoughts...cheers, mark