I noticed that there was a cut tube on my blow-off valve, it looks like someone tapped off the main tube with a smaller one, but then never connected it. When the car is idling, there is a small amount of hot air blowing out of it. Is this normal? Can someone with a 08 STi check their car and see if it is set up like this?

 

that location of where it was T'd looks like it used to have a boost gauge of some sort. at least thats where mine is cut, and that tube leads into the cabin to my boost gauge. if you're not gonna hook up the boost gauge, remove the T and connect the two hoses with a barb fitting.

 

Okay, that makes sense. It had a boost gauge before the dealer removed it. I am guessing that it should not just be venting to the air?

 

that is correct, that hose should not be venting into the air. it should be sealed. for a quick fix, you can find a screw that fits until you get a barb fitting to connect the hose back together (without the "T")

 

Alright, I have a barb that will fit it. I will likely end up putting in a boost gauge anyways in the near future.

 

That's a manifold vacuum line. It should definitely be sealed, but also you should not be feeling hot air coming out. At idle there should be vacuum on that line so you should feel suction on it.

 

I sealed the tube today, and it seems to have made a big difference to the performance of the car. I am not sure if it is just a placebo effect, but the car seems to pull harder at lower RPMs, and I have averaged 3mpg higher today than previous days.

 

good call, why didnt the dealer keep the boost gauge on? thats stupid