you dont now if the turbos were spot on in the first place fella
clean all the boost pipes and inside the a/f meter DO NOT PUSH THE FLAP DOWN clean from the boost pipe entry
check that when you remove the the vacum pipe from the breather that the little bit sticking up from on the inlet is not blocked
try blowing down one of the breather pipes to c if their is any blockage clean the pipe first as you dont want to get oil in your mouth
if all fails try venting to atmosphere (properly with a good breather) as this removes the old breather so it doesnt rely on vacum as much
have you checked the plugs to c if their is any oil on them
or if all fails try a compression test might be the rings but a lot of what i have just said is alot cheaper than a rebuild