Here are a few of the popular filter ratings for flow.
HD stock - 171 CFM
Stage 1 Big Sucker = 200 CFM
Stage 2 Big Sucker = 250 CFM.
Kuryakyn Twin Velocity = 270 CFM
K&N E-3014 = 248 CFM RK=3009 kit
K&N E-3037 = 301 CFM RK=3910 kit
HD-0800 = 231 CFM SE replacement <stage 1
Doherty Powerpacc = 287 CFM
SE Air Cleaner = 287 CFM
Zippers = 321 CFM
Woods Carbs = 4 models 135 CFM up to 340 CFM
Wimmer V02 flows 255 CFM
BC Gerolmay Overflow = 800+ CFM
HD stock - 171 CFM
Stage 1 Big Sucker = 200 CFM
Stage 2 Big Sucker = 250 CFM.
Kuryakyn Twin Velocity = 270 CFM
K&N E-3014 = 248 CFM RK=3009 kit
K&N E-3037 = 301 CFM RK=3910 kit
HD-0800 = 231 CFM SE replacement <stage 1
Doherty Powerpacc = 287 CFM
SE Air Cleaner = 287 CFM
Zippers = 321 CFM
Woods Carbs = 4 models 135 CFM up to 340 CFM
Wimmer V02 flows 255 CFM
BC Gerolmay Overflow = 800+ CFM