That flutter noise I believe is normal. The filter is fit pretty snug, I highly doubt there's something rattling. I'm sure it's just the air being sucked in causing that flutter sound. To me the car just sounds more like a v8!
I can definitely feel a difference with this filter + RPi scoops installed.
2009 E92 M3 | Alpine White | Black Extended | Advan RS | Turner Test Pipes | Dinan Axle-Back | OETuning | Eibach Springs | UUC SSK | VRS Front Lip | VRS Type I Diffuser | Matte Black | RPi Scoops | MS Filter | Yokohama AD08 | F1 Pinnacle
Special Thanks: Gintani | OETuning | eAs