The Volvo whine has to be design of intake or exhaust since at least mine is a Garret Airesearch, very similar to the ones on some MBs. I'd guess the air cleaner and associated piping design or intake manifold.

I didn't know about it until I got mine fixed -- no whine when I got the car (no horsepower, either!).

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!