Turbo issues.... or not??

[Rossie Priory]

Hi, I've a 2 litre TDI B7 that displayed originally the engine warning light AND flashing coil light. I know that once the flashing coil light goes on it disables the turbo.

My mechanic was/is sure this is a sticking turbo vane issue due to build up of carbon (125k miles) and said to try a turbo cleaner which I did (Forte).

Now when I start the car I usually get the flashing coil but if I restart the car it goes away and car runs perfectly.(engine warning light still on). Mechanic still thinks it is a sticking turbo but I'm wondering if it could be something less expensive. Anyone any experience of this?

Thanks in advance.