i experienced similar problems with my old fabia 1.2 tsi 105. it needed the software and turbo plate upgrading before the problems was cured but even though the car was driven lightly (family car as in your case), during plug changes we checked the turbo and found that the seals were leaking oil quite badly. the car had done only 80kms (about 50k odd miles) and it shouldnt wouldnt happen on an old 1.9 tdi, but i think these smaller tsi engines are too highly tuned to be reliable over the long term. dont think youll see too many do 200k like the older turbo engines could.