Engine breathing

["David Sims" <dmsims@domain.elided>]

At the rear of the left hand rocker there is a pipe which runs for 9 inches
and terminates in a small 2inch cone "filter". When hot engine gases can be
seen coming from here

Someone has commented that this is testricting the engine and I know its not
standard (put in presumably when rebuilt by PO)

In the parts catalogue the engine breathing hoses (european) are only shown
for a MKI (old 2 pipe air cleaner) and mine is a 76 MKII

Comments, suggestions welcome