Vac lines

Do those vacuum lines that normally go to IC have to be on the turbo side of throttle body?
Mainly the big one that feeds the firewall block.
The little one that loops from IC to turbo inlet, what the heck did that do?

Reason I ask is I have that plugged and the other big hose going to intake vac source.

Still can't plug in my IAC due to hi idle and just reset TPS yesterday, WTF? Why would this go outta wack already?

The hose from under the vacuum tree to the IC fitting and the hose from the same fitting down to the compressor inlet are part of the alternate vacuum source for the cruise control booster. When the intake system (and vaccum tree) are full of boost, a small amount of boost escapes through the intercooler fitting and is fed back to the compressor inlet tube. In the process it creats some vacuum in the hose going back to the cruise control booster by virtue of the venturi effect.

The vacuum tree is fed by the big hose from the fitting that is on the top front of the upper intake. Everything else attached to the vacuum tree "sees" what ever the vacuum tree sees, either vacuum or boost. Some systems have check valves in them so that only vacuum and not boost, get through. The Cruise control is one of them. If boost gets to the Cruise control it can become fubar.

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