The oil is just from blow-by gas and will be variable depending on mileage and engine condition..unless a turbo seal has gone allowing oil into the intake,
however if you have a hole in the intercooler that is leaking oil you need to repair or replace it..that is probably where the whistle is coming from.
I suggest you get it inspected by a mechanic before spending cash on parts.
If the intercooler's split, change it or fix it temporarily with epoxy putty after a thorough clean with brake cleaner or something similar....
If you haven't started pouring in litres of oil to keep the level correct and people behind you aren't choking when you accelerate away from them, your turbo's OK and it's just a normal level of contamination in the cooler from the crankcase vent.
The WISTLING noise is a turbo charger bearing been told my local mechanic, also he said it can go down at any time. Is that a big problem that better to sort out now or shall I wait till it will go down and change a turbo charger? Thanks