While driving (300D Turbo Diesel) at 2,700 RPM I hear this sound of pressurized air or something like that, not sure what it is. It starts at 2,700 RPM in 1st gear and keeps going until 2nd and 3rd gears. It gets louder and louder as the revs rise. Anyone know what it could be ?

Sounds like a pressure leak from the turbo or intake area. Look for a loose plastic line(intake area) or rubber hose at turbo wastegate

Thanks