Whisle Sound(Turbo?)

When the car is still cold I hear a whistling sound at 1500rpm. It gets more frequently even if it is warmed up and driving slowly. I don't hear it when driving at speed.

Is this the bearing from the Turbo?
Can I add any treatment like prolong to treat the bearing? I had a noise on my old Audi (Tappets) and after using prolong it when silent.

Please assist me in you expert advice.