what is the state of your front tyres? i thought my tracking was out but in the end it was the thread on my tyres. they were worn on the outer edges. since fitting new ones yesterday the car goes beautifully. seems a little thing i know that the lack of tyre thread is the culprit but it could be. mine vibrated at seventy round sharpish corners on dual cariage ways, even worse when on over run.

hope this might help.