The VW specialist did a VCDS scan and it just comes up with overboost code and too much airflow so it pumps in diesel to match and overfuels the engine hence the black smoke when revving. They said everything else tested ok, vacuum pipes etc.
I thought it could be a blocked cat (with all the lost water going through the engine when the EGR cooler went) so Ive replaced that now and its exactly the same - limp mode on hills.
Ive ordered a boost pressure sensor as thats pretty cheap and about the only thing I havent changed. Its got a new bosch MAF on but maybe thats faulty giving false air flow? If it was then disconnecting would be a good test I think as it would use a default value and then not overboost?
About £700 spent now on parts and still got the issue...
I dont think the intercooler or pipework could cause the overboost problem - pipes dont seem to have any splits in them. I did blow a few joints but thats because I didnt locate the spring clips properly - Ive screwed them together now so theyre secure...
