Warm air intake or Breather tube?

[gdupl0ck]

I have seen a number of images of early 911's with a rubber pipe connecting the smaller air intake to the right side of the bodywork in front of and below the oil filler as shown in the attached 911E image. My 911L has the aperture into the body member but never had the connection to the air intake.
Can anyone throw light on which models this pipe should be installed and what it's function is?

Thanks