Performed boost leak test, heard popping noise inside valve cover

[nestamon99]

I will assume that the seal inside the turbo took a crap. When I performed the boost leak test, I removed the hose from the TB and capped opening. Then I pressurized intake system through the turbo inlet and when I did this, a popping noise could be heard from valve cover. The turbo only has 2989 miles on it. How is it possible for a turbo to leak air internally to the exhaust system?? There's absolutely no oil buring

 

[pj91gsx]

maybe valve seals.

 

[nestamon99]

maybe valve seals.

Thank you for your input.