Advise please- have a 2001 E55 which has had aworsening banging sound that seems to come from the right rear of the passsenger compartment-it sounds like something BIG is loose- my dealer has aleternated between saying"with the stiff suspension and performanse tires this soun is normal" and replaceing things ie. the entitre sunroof assembley and then the headliner- the noise is only getting worse- it is absent on most smaller bumps but a lagr or sharp bump sets off either one LOUD smashing sound or a series of closely spaced loud rattles as if it were an SUV with the rear hatch ajar. My dealer seems to want to make chrgeable changes rather than SEARCH for a problem(they do not get paid for searching!) Thanks for any help.