item 4, the part is called a breather hose. there are 4 of them, this is the one that goes from air cleaner housing to ___. it is like $12. If I were you I'd replace the other 2 breather hoses in that area that are easy to replace (the other one is under an injector and much harder to acccess). all those hoses are likely petrified and don't seal as well as new soft rubber hoses, you will be amazed at difference in feel of old vs. new hoses.

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2005 Mercedes C230k sport sedan, 6 speed
1987 Porsche 924S - 968-engined track car