It is for the turbo boost solenoid near the master cylinder. Just replace the line, also remove the "banjo" bolt it attaches to at the intake manifold to check that the banjo bolt passageway is clean. The banjo bolt has two sealing washers, don't lose them. Until it is fixed the car will have a lot less power.

Can you splice it together temporarily with rubber hose and clamps?

Please include year/engine/model when asking for help, it helps us help you.

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