I've been trying to track down what I think is a boost leak. I get the overly audible whoosh sound under boost.
In the past I made an adapter to fit into the hotside hose and pressurize the plumbing up to 25psi. Usually it would hold pressure for 10-15 seconds then bleed down slowly. Now it starts to bleed down in 2-3 seconds AND pressurizes the intake manifold. Seems like the throttle body is allowing pressure past it??? Has anyone seen these fail and/or the plastic intake manifold crack?

 

Yes, this is a common problem. Just one of many threads:

https://www.northamericanmotoring.co...-manifold.html