my bet still on a boost leak,
engine and working turbo are unlikely to cause the symptons your describing.
however if a cooler pipe expands under pressure exposing a leak,
then it all escapes thru the leak, cause its the path of least resistance. ie not compressed.
the air flow metre is reading normal because it before the turbo, so it thinks your on boost and therfor tells the injectors to start pumping lots of fuel.
however the engine isnt injesting this air due to the leak so it suddenly goes way rich. like 6 to 1 afr's.
hence all the smoke, minimal boost , and running like crap when on boost.
presurise the inlet sytem before you pull any more apart.