sorry i cant quote, internet too slow.
but Micheal said where does the air go? if its not vented it stay in the pipe.
You're right where does it go? it pushes back to the turbo thats the only way it can go. if you got 12 psi in an enclosed area it going to go back the way it came. its just not going to stop and sit there and wait for the butterfly to open back up. the turbo is going to loose rpm then its going to have to spool again.