Air gushing internally from intake plenum after turning off engine... normal?
 

This is just a sanity check with my turbo car. When I turn off the engine, I can hear air gushing internally from the intake plenum area. It's muffled, so it doesn't sound like it's gushing outside from the gasket part.

I'm trying to see if I have a boost leak. I can't get the car to push over 7 PSI (3rd gear pull to 5k RPM at WOT) after installing the MBC and giving it a full 5 turns. I gave it the 6th full turn, but have not tested it yet.

Its just the vacuum in the manifold slowly equalizing to ambient pressure.

They even do that when NA.

Thanks! I didn't notice it before, so I just wanted to make sure this is normal.