I have a 2004 93 2.2TiD and I am just curious what the whistle noise is everytime I change gear. It sounds kind of dump valve like but diesel turbos don't have them do they? If antone knows what it is, can I make it louder??
You have a variable nozzle turbo where the turbo vane's pitch is controlled by a vacuum diaphragm capsule. When you drive the pitch of the vanes are being varied to stop the turbo stalling or over-reving. When you stop the car, the pressure in the capsule is released and you hear a phssst noise.
The whistle could be related to that, or could be related to electrical interference from the engine on your stereo.