It's still not clear to me.
I am aware of the stuff you listed as 1 and 2 some of part 3 i don't quite get. But i know it's unusual with a butterfly. Is the butterfly the reason for this tube?
i guess it's obvious that there is a vacuum in the hose when the butterfly closes because it comes out after the butterfly.
But, there is a small pipe to let air through at idle..to small for higher rpm's, hence the vacuum as the engine revs down..
But when adding a turbo and boost I'm not convinced there will be much of a vacuum even with the butterfly closed..
If I move it to somewhere after the turbo like you said maybe i can just leave it as it is? is that what you are saying tapage? have you got some pictures of your setup?
What does the vacuum actually do to the pump?
