If you don't mind me asking, how's the sound and power with the Yoshimura + Flapper removed? I'm trying to decide about going that route or getting the FMF Q4. Thanks in advance!I am running the Yoshimura with a K&N filter and the airbox flapper removed. I have not had a single pop and the bike has great response. Eventually I will do the power commander but I dont think its really needed, however, I wont remove my airbox lid until the PCIII is in. I have not dyno'd it yet to check the mixture but it cant be too far off. I am basically at sea level here in new jersey. I have quite a bit of experience with bikes, i've been in the business for 17 years have a red level honda tech certification and a five star yamaha tech certification.