You can check the turbo out with the engine cold. You have to remove the intake
air duct and the center air hose going to the turbo. Be careful not to get any dirt or stuff in there. Once the hoses are removed you can reach inside the
turbo and spin the shaft and check it for play. If there is too much play the
wheel can hit the housing. Mine started making a whistle like sound and when
I checked it the wheel was hitting the housing. If you run it too long like that the wheel will destruct and break all apart.

Dave 82 242ti 278k mi.