TDI4 Engine fault light and smoke

Hi, I have a 04 TDI4 which has developed an engine fault light at high speeds ( above 70 and also slower speeds going up hills ) I had a diagnostic check at a 4x4 specialist, who thinks it is turbo related. They changed the wastegate modulator, but the light still comes on from time to time.

Today I noticed it smoking quite badly when accelerating, white mostly I think.

Looking at another post I have examined the intercooler pipes, one of which has a spot with some damage, although I don't think its actually perforated...

Any Ideas?