Yes, the highest pressure will be at the discharge of the turbo. There will be some pressure loss in the pipes and more through the aftercooler. So the lowest pressure will be entering the inlet manifold. Why the after market BOV ? Isn't there already one in the system somewhere ? Others have described the Tssssssssssssss sound on upchanges, but it's hard to pick unless there have been some mods done, like after market air cleaner etc.
Link doesn't work.
So do you have a recirc valve or a dump valve? Either way the pressure goes through the bottom of both. If you have a dump valve then the gets released into the engine bay, if you have a recirc valve (like what youve shown us in the first link) then its goes back into the intake