Done new head gasket, engine runs great at idle. Fault code stored 2B63, fitted new cam sensor to exhaust cam code still there. When engine is reved to 2500- 3000 rpm, vibrates in what appears to be the valvetronic cover/ rocker cover, chugs out smoke then comes to a screeching hault. have rechecked timing, but can't seem to find a fault. Any thoughts please