2004 CR-V P0497 Code: High-Pitch Whistle at Highway Speeds - Possible EVAP System Vacuum Leak?

I've been experiencing a persistent P0497 diagnostic trouble code on my 2004 Honda CR-V for the past 2 to 4 weeks. Recently, I started hearing an intermittent high-pitch whistling sound, which occurs primarily at highway speeds. The P0497 code indicates an EVAP emissions system low flow condition. Given this symptom, I'm wondering if the whistling noise is caused by a vacuum leak in the EVAP system and what common components might be responsible for such a leak. Any insights or troubleshooting steps would be greatly appreciated. Thanks, Nor Mats