It is a BREATHER HOSE, part 103 094 10 82

How the air intake does work?
If air does not go through an air filter but bypass through a crack in BREATHER HOSE it is still the same air.
What does the vacuum do? Why does a car need it?

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I checked my O2 sensor 3 times - 2 times after driving for 40-60 min I got constant 0.30-0.32 V on any rpm. But the first reading from cold start was 0.7 V ??
I am going to test the sensor with propane today.

>>c. Artificially enrich the fuel mixture by directing propane into the intake until the engine speed drops by 200 rpm. Or, if you're working on a vehicle with electronic fuel injection, you can remove and plug the vacuum line to the fuel pressure regulator.

Where is the vacuum line to the fuel pressure regulator?

>>a. Induce a small vacuum leak.
b. If the voltmeter rapidly drops to .2 volts or below in less than a second, then the oxygen sensor is correctly measuring the lean mixture. But, if the voltmeter responds sluggishly, or if it stays above .2 volts, then the sensor should be replaced.

How to induce a small vacuum leak?


Thank you for your help.