vacuum connections at the brake booster and clearly showing the vacuum one-way valve (blue)

This is the flappy control relay that actually connects the vacuum supply to the flappy. It shows the line to the flappy plugged, probably because of a leak under the intake. A vacuum line to the flappy actuator should be connected there.

vacuum distribution point at rear of the engine.

 

VACUUM LINE DIAGRAMS S3.pdf

VACUUM+LINE+DIAGRAMS+S4.pdf

The 4 way fed from the brake booster has 4 connections:

- vacuum feed from brake booster via check valve
- vacuum feed to hvac manifold
- vacuum feed to flappy valve solenoid switch
- vacuum feed to vacuum accumulator (egg box thing behind the wheel well)

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This tool will help a lot finding vacuum leaks. Porsche P9160, Mityvac is the supplier.