although it looks corroded if it isn't leaking it's probably best to just give it a thorough clean. They are an interference fit, the same principle as the valve guides. So if it needed replacing I'd take it to a machine shop and get them to carefully remove the old pipe. VW don't list this as a separate part of the cylinder head so you could work out the correct diameter of pipe needed for the interference fit, cut a section of this pipe, and then put a slight flare on the end so the hose has an edge to seal against. You could then fit pipe into the cylinder head using a wooden mallet or simi