I have a 2005 Chevy Equinox, when the vehicle is idle there is no noise at all. The Whistle grows louder as the engine speed increases.
Check all the pulleys on the engine (including the alternator) for bearing wear. Belt removal is required. (The ‘whistle noise’, it may not be)
Check all the vacuum hoses for looseness or cracking.
Also check to ensure the air intake clamps and hose are tight and in good condition.
Make sure all the plenum and intake manifold bolts are tightened to the specified torque requirements.