Originally Posted by Jeff@topgearsolutions
As far as turbo's going out, smoke out the back is a common culprit, elevated Wastegate duty cycles are another, but one would need to ensure their are no boost leaks before blaming the turbo's.
Siren noises CAN be a common characteristic on this car. It's a tiny fan blade that spin's 10's of thousands of RPM's, it's going to make some noises. Obnoxious sire noises at light cruising when the car is full warmed up, along with elevated duty cycles to reach boost target and or oil consumption or smoke out the back may be a sign of turbo failure.
If your car is running like a champ, don't worry. If you have some smoke out the back it does not necessarily mean your turbo's are on the way out either.
Every scenario does not have an A + B = C
One must encompass many details before singling out that one symptom = one failure every time.
Your best bet is to start datalogging. If you don't know how to interpret the logs, post em here & we'll be happy to point you in the right direction.