as read on charlies blog : http://vw-type-3.blogspot.com/2006_12_01_archive.html
You replace one of the crank case bolts with a special one with a spindle attached onto one end of it. the throttle linkage then hooks onto the spindle and there is one extra linkage in the circuit. Can’t say I’ve noticed any difference but it’s a “nice to have”
vw1500s 