Intro: Whistling noises usually mean air is escaping somewhere.
1. Loose window seal
Wind whistles through gaps.
2. Roof bars
They create wind noise at speed.
3. Air intake leak
A split hose whistles under acceleration.
4. Door not fully shut
Even slightly open causes noise.
5. When to check the turbo
A failing turbo can whistle loudly.
Summary: Most whistling comes from wind leaks or air intake issues.