Hi there,
I'm busy building a highly detailed RB26 engine (Tamiya) for my R33 Skyline (also Tamiya). I use loads of reference pics to make the detail look perfect. Still, the reference isn't good enough. Could anyone please explain me what the thing in the red circel is, and where it comes from (or goes to). I don't know where to connect the tube you see

I'm sure some of you guys know the answer.
Thanks in advance.