Newbie needing help on Engine pipe

[Bednortan]

Hi, I had a broken dipstick tube on my 96kw B5 2.0 2004 Passat estate so I changed that (with difficulty because VW put a manifold in the way). I noticed after I changed this that a plastic pipe under the engine cover had split in half. I have taped it up for now but I need to change this tube but don't know what it's called. Can anyone help?
Here's a picture and the pipe is arrowed at top and bottom.
Thanks in advance
31660