Scirocco Register

My 1.6GT has an issue where the revs will stick at around 3k rpm. Sometimes it does it, sometimes it doesn't. Had a look and there's a diaphragm that pushes a flap open on the left hand side of the carb (opposite side to the throttle) and when I press this the revs drop.
Few places have suggested vacuum leak on one of the pipes or an o-ring that needs replacing.
Has anyone got a bit more info on how to rebuild the carb? Or would I be better off spending the time converting to something like a twin webber?
Thanks, Liam.

As you'll find when looking around the forums, not many people know how to work on these so tend to switch to a Weber dmtl 32/34 as they're simpler to work on. Or if you want to stick with it there is a service manual here: http://vwa1.dadoghouse.com/wp-content/u ... uction.pdf