I understand that this is very rare occurrence of out of balance. The driveshaft shop did find it out of balance. They balanced it as mentioned and still issues at higher speeds. I was really hoping this 1 piece would be the ticket as I read a lot of great reviews on it. I know many coupe folks are happy with it...I don't know however if there are many 2+2s with the 1-piece. I will contact Z1 on next steps. I would want to mention that I have ordered many parts from Z1 over the years and never had a problem and the staff has always been responsive. Will keep you posted on the next steps. Thanks again everyone for the suggestions and advice. This board has always been helpful.