my cl-s makes humming noise when im at red light once in a while , im thinking it might be because i have an aftermarket fuel & water seperator ? i had to put an aftermarket because dealer was to packed and needed car right away, / my cls makes rattling noise when i put in reverse maybe my aem cold air intake is loose ?

 

Not sure about the humming noise, although the rattling in reverse is probably your intake. Mine did the same while in reverse. The bracket on the intake has some adjustably in it. Loosen the bolt on the bracket then push on the intake toward the motor while tightening. If the still does not work, you can wrap the intake with some type of rubber or something that would keep it from rattling.

Brad