My Synapse DV sounds exactly like that with the preload maxed out. It's a 90s sound, it's slow and obsolete, but I like choo choo choo more than pshhh.

 

That is the sound of your turbo fluttering, if you want that sound you can chuck the bov and seal that gap air tight.

But I would not advice so coz it strains the turbo by pushing air backwards to it when u shut the throttle. (my opinion)

Either your bov is on backwards or the spring inside the bov isnt working as it should.