Whistling noise in engine?

Sounds like a vacuum leak. Check with 2'-3' section of hose and put one end to ear and with the other check all over engine for the amplified suction noise.

Does the noise occur when moving or stopped? Does it change with engine speed? If the whistling changes when pressing and releasing the clutch pedal, then probably yes.

Does the noise change with rpm? For clutch noise I would suspect throwout bearing when the engine is idling, transmission out of gear and your foot off the clutch. Bring it by Milt's today and let Adrian look at it.