Sounds similar to the issues I have been having!! I have just had my van delivered back tonight so the info is hot of the press from the mechanic, (VW reteration guy) who knows what he is doing and talking about!!
Internal fuel filter completely clogged with years of silt and dirt, was removed and completely cleaned out
Fuel tank completely flushed out
External fuel filter replaced! He cut it open to show me and I have to say I am totally shocked any fuel managed to get through, it was horrendous!! I am waiting for him to send me the photos over and if I get them I will post some up here.
Fuel pump replaced as it was reading a bit low on the pressure.
All fuel lines replaced just to make sure.
Now this is the strange bit, basically at some point in time of it's 41 years of being around, the ignition switch went, so the rather clever owner fitter a toggle switch that basically connected between the ignition barrel and switch to by pass it, why who knows..... Basically one of the wires was bare under the dash and while the mechanic had the engine runnning and he was under the dash tidying up the wiring, he touched this bare wire and the van died.
Oh and the other thing you may want to check is the coil. I spoke to Just Kampers and the guy told me to take it off, give it a shake and if it sounded like a can of coke, it was knackered, it did exactly that and so replaced it as well.
So it might be worth having these checked out just to make sure!!!
Good luck with it.
GOM