Engine Noise

[sundodger 0]

My engine makes what I can best desribe as a whistling noise, which seems to be coming from the engine area (as opposed to the serpentine belt), its not always there, but is now becoming more regular. I've found and fixed a couple of air leaks already.

The car also intermittently stalls on slowing down, but will idle okay on restarting although I think I've fixed this but not sure till I drive to work tomorrow.

Could it be the inlet or exhaust manifold gaskets? Any ideas would be of use.