TDI Injectors: 2.7L & 3.0L V6 Engines

Hi,
"Elsewhere, I have often read about faulty injectors in V6 TDI engines. Specifically, those manufactured up to approximately x/2006 are said to be affected. Apparently, a coating is coming loose, which results in the injectors no longer sealing properly."
Does anyone know anything about this?
Is it possible and worthwhile to only replace the nozzles in order to limit costs?