Hi guys!
2012 MINI R60 Countryman S ALL4 with 47k miles.

I will hear constant-tone whistle noise from centre or passenger side (I am not sure, because it's hard to locate) only in two cases:
(1) Shortly after I start my car in the morning and drive at the local road. When I move my feet away from throttle, the whistle noise comes out. After I depress the throttle again or the car gets completely stop, the noise goes away.
(2) When cruising at around 70mph, the noise will come out when I don't depress the throttle (the engine is idling). The noise disappears when the speed drop to around 65mph.

I got CEL on twice before I began notice the whistle. Both CELs come out when I was cursing at highway with around 70-75mph and I did not feel anything abnormal on engine (reduced power, vibration, etc.). Finally I got the CEL code 2C57 and got my turbo charger replaced under California 7/70 warranty.

I assume it will solve whistling problem, but it only reduces the noise level of the whistle and makes (1) happen less frequently. And the sometimes noise will still come out.

So my questions are:
1. Is it possible that MINI dealer replaced the faulty turbo charger?
2. How to tell if it's due to vacuum leak from valve cover? Mine valve cover does leak oil, but not too many. (I replaced valve cover gasket a month ago.)
3. Since the noise won't come when the car is standstill, is it safe to drive without oil cap to see if valve cover is leaking vacuum?
4. Is it possible the water pump is leaking?

Car inspection report provided by dealer.


Thanks