Hi.... i have the same issue, when i Rev my car, or go on ueven roads, there's a metal-like rattling noise. Tapping on the steering wheel produce the sound, right?
If yes, You try open up the plastic cover covering the meter. I open up mine, and just touching here and there, touch behind the meter panel and all wires you can touch. I did that, and the noise is gone now.
For the AC Ventilation, it's the air cond vent plastic clip where you hold it to slide the fins right/left / or up/down. Dismantle the clip from inside , with a screw driver (philip) and you will see two holes. Poke and twist to open up the clip, add some tiny bits of sponge in there , not too thick or thin, just right, and attach the clip back up snugly.
Can you describe the sound if it's not what i mentioned?
You are right on ac ventilation. It is the fins that make the sound. Thank you for the solution.