I agree with the suggestions that it is most likely a head gasket problem – I don't think it is a turbo or a piston ring problem. In my, somewhat limited, experience the VW TDI turbos are quite long lived. I've currently got two that are both closing in on 500,000 KM. So I would focus on the head gasket. I'd also suggest contacting VW to see if they might extend warranty coverage, 85,000 KM seems way too soon for a head gasket failure.
With such an early failure, make sure to try to find the reason. The head and block deck should be checked for flatness and it would be good to check the head bolt torques before pulling them. What you don't want is to just have the head gasket replaced and to assume that that will fix the problem. The only time that will be the solution is if the head wasn't torqued down properly. Even then you'll want to make sure there hasn't been any erosion of the head or block that would cause the new gasket to fail.