I have a wind or vibration noise at higher speeds mostly above 60 mph at the inside rear view mirror. When I push hard with my fingers at the black plastic cover behind the rear view mirror ( I guess this is where the OnStar components are) it stops significantly. Its the craziest thing I've ever seen. There dosen't appear to be any way air could get into this area. The windshield seal looks fine. 2013 LT2. Sounds nuts dosen't it? Any input welcome.