vacuum whine

[browrz]

Typical scenario:
Car warmed up, give it some, lift off and then get very high-pitched whining noise that sounds like a vacuum-sucking rather than a air leaking out (if you see what I mean).

Is coming from the plenum area and disappears when engine settles after heavy load or when you accelerate (even gently) again. Is it something like a leaky plenum gasket? Is this a problem?

Any ideas?

[whitey]

I had a similar noise on my Chim 500. It was an intake gasket leak that eventually completely went, spraying out water, overheating and a nice trip back to dealers for new gasket.

[2 sheds]

Sounds like manifold to head air leak, check that the bolts are tight.
tim

[mojorider]

Mine does this also, just from cold. Once warm seems to go away.

I have a 98 (450) with 42k on the clock.