Chrysler Repair: Engine Noise: 2.5L turbo upon decceleration, vacuum device, dodge spirit

Question
I have a 1990 Dodge Spirit with the 2.5 liter turbocharged engine.  For the past couple of months the engine has sounded like an iron lung, whenever I let up on the gas.  The noise started suddenly and hasn't gotten any worse.
I've listened under the hood, but I couldn't pinpoint the source of the noise.  The car runs well, but I'm concerned that something important might be about to go.  Can you give me any idea what this strange noise might be?  Thank you for your generous help.

Answer
Hi Herb,
I assume you mean an air sucking sound. My suggestion would be to use the underhood diagram, which shows all the vacuum lines and the connections to the intake manifold, as a roadmap to trace all these lines seeking either a break or disconnected line or perhaps an open vacuum device like the waste gate on the turbo. That is the main system associated with the intake of air so it is the most likely source of a new noise. I haven't personally owner a turbo and thus have not experienced this, but that would be my best guess.
Roland