||to cause a "squeal" or "whoosh". A leak from the gasket usually comes because the gasket got moved out of alignment in the tightening down process, therefore it doesn't seal like it's supposed to. In some cases the gasket can be torn in the process. If you discover yours is this way when you pull the plenum, you'll need a new gasket.
When you go to re-install the plenum, stick a phillips head screwdriver down in the bolt holes while a helper helps hold the plenum slightly above the gasket. Then you can nudge the gasket into proper alignment with the bolt holes if necessary.
Make sure nothing is preventing the plenum from sitting down tightly on the lower plenum too... like the vacuum line bracket that has the dual curved shape around the bolt holes, and the bracket on the driver's side. If that shape doesn't fit exactly into the mold for it on the plenum, that can cause it to sit up just enough to cause a leak.