04 cupra tdi turbo/oil pressure

[Captain Sausage]

Hi,
I've got an 04 cupra tdi.
2.5 years ago it blew a turbo, which was replaced but this brand-new unit has blown again.
This time I've bought a core which has been fitted to the car and I've been running it for maybe 100 miles without nailing it.
Here's my worry.
The turbo is noticeably loud the second I lightly blip the throttle. Say maybe 1200rpm and its whirring away. This was exactly the same as the last turbo, which friends would all tell me was about to go (and they were right).
So, I'm sat here with 2 broken turbos in less than 3 years, and another new one not sounding happy.
Could it be a knackered oil pump, and if so where is it and how easy to replace.
Hope someone can help, cus the cars making me miserable. Thanks.

 

[cheshire cat]

did you also fit a new oil feed pipe?

 

[Captain Sausage]

It had a new one last time.
It still looks like new and it definitely is allowing oil through cus it was leaking oil on initial startup which was traced to the feed pipe from the turbo being slighlty loose. That's all sorted now with no oil leaks.
I'm thinking there could be restriction somewhere (but where?) or low oil pressure.
This high pitched whirring from very low revs, could it be an air leak or would it be a bearing?