turbo whistle sound when driving (on gear)
 

I have a 2002 Jetta 1.8t GLS, 5 speed and its making the whistle noise when I am driving from very low rpms (~1000). Right now the car has no power and another weird noise in high rpms. It only happen when I am in gear. If I push the clutch in and press the gas, the turbo whistle sound comes in high rpms (~<3500). What would be wrong with my car, please help?
belt, gear oil, ..????