Hello. Hope to get some help. I have a GLC300 I took delivery in February and currently have about 3,000 miles on it. The vehicle has many silly little problems and shortcomings. My feelings is it needed more development time. But on to the newest problem. It has developed a high pitched whine. It starts at about 70 mph and builds in pitch and decibels to about 75 mph then tapers and is gone by about 77 mph. The noise seems to be coming from the rear. I have Pirelli Scorpian Verde run flat tires. Any ideas?