I'm not the original owner of my 1999 ml 430, and when i picked up my vehicle i noticed the trim around the windows were discoloured, or whitish, probably old built-up wax... I've tried for months to remove all this build-up...It goes away intially, but it always returns.... I've also seen this problem on other ML's.... any advice on how to remove this stuff for good....or any good products to use...thanks...