When driving,(300D Turbo Diesel) around 2,700 RPM there is this sound coming from the engine compartment, from the right side (I think that's where the turbo is)and with the window down I can really hear it. It sounds like pressureized air escaping. It starts at 2,700 RPM in 1st gear and keeps going until 2nd and 3rd gears. I'm thinking it could be something with the turbo, but there hasen't been any loss in performance. The sound gets louder as the RPM's do.

I don't have any experience with MB turbos,But I used to own a 79 mustang 2.3l turbo.(my first car) That car had a whistle type sound when the turbo kicked in. This is just a guess, but maybe 2700rpm is when the turbo is pressurized. I could be wrong. andy