Boost Leak Testing - burbling sound

[S4Flyer]

Been tracking down a boost leak in my 1.8. VAGCOM shows me getting no more than 8 PSI, when requested is closer to 12-15.

I've done what this guy does to test for leaks: https://www.youtube.com/watch?v=AA-p_Bd5DKQ I've disconnected/blocked/opened all the same things he does.

Problem I'm having is that the engine is making a burbling noise when I pressurize the system, and it's very hard to hear any potential leaks.

Am I missing something here, or do I have another issue? I know the test will apply pressure to the engine internals, but none of the videos I've watched seem to have the engine making the burbling noise.

[old guy]

The turbo oil seal is normally exposed to a vacuum from one side and oil pressure from the other side. When you perform a boost pressure test through the TIP you are applying pressure to the typically non-pressurized side of the seal combined with no pressure from the normally pressurized side. Consequently you get pressure blow-by into the oil line. This produces the gurgling sound that you are experiencing. Perfectly normal.

[S4Flyer]

The turbo oil seal is normally exposed to a vacuum from one side and oil pressure from the other side. When you perform a boost pressure test through the TIP you are applying pressure to the typically non-pressurized side of the seal combined with no pressure from the normally pressurized side. Consequently you get pressure blow-by into the oil line. This produces the gurgling sound that you are experiencing. Perfectly normal.

Thanks for the explanation!