WTF?!?!?! Vacuum line through firewall??
 

I've been having vacuum problems that have led to an inconsistent idle since I got the car running a week or so ago.

I also discovered several oil leaks, probably due to dried out gaskets and such from the car sitting for a while, so I'm in the process of dropping the engine to go through it an replace the gaskets, belts, etc.

In the process of disconnecting the harnesses along the firewall in the engine compartment, I noticed a "Y" on the purple vacuum line that runs along there and that it has a hose that routes through the firewall into the cabin smack dab behind the back of the motor. Any ideas what the heck that would be for? Never would have seen it had I decided not to drop the motor.

Operates the vacuum motors in the HVAC system (under the dash).

As George said.
Having dropped and installed the engine lately, there are two lines.
One with a Y is the vacuum source.
The other line operates the heater valve.

OK. Glad to know I'm not crazy. I was really thinking the PO was doing some odd stuff. Love how porsche doesn't really include this info on the vac routing diagram, either. It's pretty damn vague.

It wouldn't be any fun if everything was spelled out in minute detail.

It's better than a toyota 4a-f diagramme:

http://alflash.com.ua/Vacuum/toyota/4A-F.gif


I've lost years off my life due to the vacuum carb system on that engine.