Sunroof whistles when driving

I would guess that your sunroof is leaking air for some reason. It could be as simple as something caught in the tracks preventing the sunroof from closing completely. It's also possible that the gasket around the sunroof has been torn by something and leaking. You seek an inspection by a shop familiar with Scion. It may be a fairly simple fix.

Actually I answered your question without signing in. It's also possible that if you live in a very hot environment the sunroof gasket has hardened and is not sealing properly.