Volvo Repair: volvo 740 gl limited edition, volvo 740 gl, intake manifold gasket

Question
i own a 1989 Volvo 740 gl wagon. 5 speed.when in neutral the idol jumps up and down. I'm on my last nerve with it. guy at Napa said it sounded like the ideal air control valve. so i replaced it but it still does the same thing.
can you help?

Answer
  Steven, I'm sorry, I don't answer american "idol" questions or "ideal" questions. VBG
  Idle questions I can deal with. It's never the IAC (IDLE control valve) You have an unmetered vacuum leak somewhere. Usually the intake manifold gasket. Take a can of carb. clean with the wand attached, while engine is IDOLING, and spray it around the intake mating surface to the head. Move it slowly because it takes a second or two to react.When the "ideal" smooths out or increases, you are near/at the leak. If that's all good, check your vacuum lines for splits/cracks or disconnections. I gaurentee you that this is the problem. Please let me know the results?

Mark