Yesterday i had the old no power after 2600rpm and heaps black smoke../limp mode.was fine untill 2600rpm then the boost would be cut and the smoke would appear.pretty embarasing...as im chipped and ive been giving the rail pressure relief valve a bit of a nudge here and there..i had a clue where to look...normally i get the fuel leak code but laitly i havnt been getting anything..mystery....i started with removing and shimming the rail valve with another 2.5mm shim.refitted it and im back to normal...
One thing i did notice was a tiny bit of white goo in the entry to the releif valve almost blocking the hole..normally this is a good thing but i think in my case it may have been unseating the internal ball just enough to make it purge with a bit of rail pressure..hence the limp mode