To stop the crankcase vapours properly (which is a VERY good idea) you need to trace this pipe and remove it from the crankcase. Remove the "anti-backfire" one way pcv valve if fitted (which is actually just a ball bearing and a spring in a tube) and replace the tube in the crankcase, running it to atmosphere or a catch tank as is your want. Then do not forget to plug the inlet in the manifold.
Griffo, could you put a link to the pictures of that in here? Or maybe some better gifted TM member could draw a schematic of where to find the second breather pipe...? We're so close to solving this "engineering masterpiece"!
