So today I decided to do a boost leak test on my D15B by attaching my adapter directly to the turbo intake and it would not pressurize at all. I mean, it all just poured directly out of the valve cover breather port which currently just has a filter on it. Is this normal?? I also later then attached the adapter directly to the throttle body and it seemed to pressurize as expected (despite a few leaky areas that I will have to look after). So being that when attached to the throttle body there is no leak, and when attached to the turbo there is a giant leak, leads me to believe the turbo is the failing area. But what could be causing this? Bad turbo seals? I'm a bit lost how the pressured air could be routed to the valve cover so effortlessly.

If it matters, the PCV valve (black box) has been removed as it routed to a sealed catch can which then exits to the intake piping. The car also had previously been blowing some smoke, so I did recently just replace the valve seals. Last compression check wasn't that long ago and everything checked out fine. Any thoughts? This really has me confused.

 

You answered your own question. A sealed catch can routed to the charge pipe is your link between turbo intake and the crankcase. Disconnect the catch can from the charge pipe, plug the hole in the charge pipe, and vent the crankcase (via the catch can) to atmosphere.

 

Beat me to it!