"Turbocharger whine is often caused by excessive bearing wear. What generally happens is that the bearings wear allowing the impellers to rub against the compressor housing of the Turbocharger. This causes the whistling during acceleration. This is not to say that all Turbochargers that whistle need to be replaced. Some Turbochargers whistle for years without failure. Frequent oil changes will help prevent Turbocharger failure!"