A few months ago, I blew my oil cooler line, when driving in city traffic. Luckily I realized it early, pulled the car over with oil all over the place. The car survived with no damage! to the engine and runs fine. However, since then the turbo has started to "whistle" when listened for carefully inside the car between 1500-3000RPM, with the noise increasing with engine RPM. There is no noticeable difference in the performance of the car. The oil change was free of metal debris. The whistling noise disappears once the car is warm and cannot be heard at higher speeds.
Thanks in advance