I have a Feel's cat back, 3" CAI flex pipe running from the grille into the OEM airbox, airbox has a 3A Racing pod inside + I have removed and blocked off the resonator chambers within the airbox. I've been told the Feel's exhaust is a bit louder than the rm01a. Its not overly loud though. I pretty happy with the power for now. I have KiddRacing headers lined up once I get bored of the power...