As far as I know there is no manual .   If you are sure that your carb is the problem, You can get a rebuild kit that has instructions.  You have to remember that this kit is a after-market item and you won't find any info in a VW shop manual. Just make sure that you don't have  other problems with the engine , valves, electrical. tuning etc. before you waste a lot of time and effort on the carb.