Hi Roobarb: Welcome to the world of VW. Your problems can stem from a number of sources which you must systematically eliminate. A sweet operating engine has the correct fuel-air mixture arriving in the combustion chamber where it is given reliable equal compression followed by a healthy spark arriving at the correct time. Take away any of these and you have a non-operational or poorly operating engine.
If pumping extra fuel seems to help the problem, suspect dirty fuel lines filled with years of sediment and gum, a weak fuel pump where the pump rod is sticking or a carb which is in need of a rebuild. Look in the throat of the carb. ( it is a stock PICT carb I assume ) In there you will find a series of double holes right in the wall of the carb. They must be free of varnish and the build up of gums etc. The holes deliver fuel to become part of the mixture. If they are plugged you will lose your idle. This is a good point of departure. Rebuild the carb, add an in-line fuel filtre between the fuel pump and the carb. Pull the fuel line off of the carb and place the end of it in a glass jar. Have someone crank the engine. Does the fuel pump produce a strong steady stream? or a lame dribble? Try these suggestions and let me know how it goes. Dan ( MY72Bug ) in Goderich, Ont.
I'd rather have a partial bottle in front of me than a partial frontal lobotomy.