im sure its to do with the air going into the carb, i think its to stop to much going in or the other way round, its not super imortant but ithats what its there for, the golf i had before the one i have now ran fine without it, if you unplug the hose coming of it then the revs should change abit, please correct me if im wrong but thats what my mechanic said its for..... i hope hes right
