Be very careful Paul.
I would look again at the injector shutting down as per kevins suggestions.
I had one of these with the self same set of symptoms, although it was on a BBY engine.
mine was slightly down on compression on that cylinder and it took me ages to work out what was going on.
In my case only a major engine strip would have sorted it (pistons/rings).I think most of these small 16v VW engines are prone to ring problems.I also think the engine management is far too sensitive on these engines.
Mine had only done 40k.
HTH

Colin