Where does this hose go?

[toddjy]

saab 9-5 2003 linear

[GeoffR]

I assume you mean the part with the red ring on the inlet pipe?
If it is blocked of it may have been modified out, if not there should be a short hose that goes under the inlet pipe and to something on the firewall. I can't see what on WIS.

[Mjollnir81]

If it’s the hose you drew red lines on I believe it goes to a T connection

[GeoffR]

If it’s the hose you drew red lines on I believe it goes to a T connection

If it is that one it goes to the bypass valve control solenoid.