We have a 1985 300D Sedan with just over 105,000 miles. This car was passed down from my great uncle who had ties with Mercedes. I have this reoccurring problem with the car. Ever since we can remember, there is a whistle just before the turbo kicks in. In the last year it feels like the car is loosing power. On anything over a minor hill, the car will start to whistle as if almost to engage the turbo charger. Right then the car looses power and slows down. If you push harder on the pedal, the car will go from third into second. Our local Mercedes Benz dealer has not been able to fix this problem. Also the car shifts hard between gears.