On the intake hose for a 2001 Honda Prelude SH there is this U shaped tube with one closed end (sorry about blurry shot):

[![enter image description here][1]][1]
[![enter image description here][2]][2]

(The tiny thing sticking up on the top left isn't a tube it's just a solid structural support piece.)

The part is only identified as ["TUBE, SIDE BRANCH"][3]. It's also discontinued for some reason:

[![enter image description here][4]][4]

What does this tube do, exactly?


  [1]: https://i.sstatic.net/nCrzj.jpg
  [2]: https://i.sstatic.net/FmnAn.jpg
  [3]: http://www.hondapartsguys.com/honda/prelude/17281p13000/2001-year/typesh-trim/5-speed-manual-engine/electrical-exhaust-heater-fuel-cat/air-cleaner-scat/?part_name=tube-side-branch
  [4]: https://i.sstatic.net/poPkq.png