I found the following comparisons of air cleaner housings ( in flowed CFM). The testing was done by K&N with oiled filter in place on a flow bench so no "ram -air" would have been in effect.
As far as bang for the buck I would say the Screamin' Eagle looks pretty good here.
H-D stock 165.5
CCI/ Halebob 197.5
Force Motor (BLK) 262.2
w/ Filtercharger cover 250.8
Force Motor ( WHT) 284.6
w/ Filtercharger cover 281.6
CCI/ Siren 330.1
H-D Screamin' Eagle 421.8
Zipper's Performance 455.6
Arlen Ness Big Sucker 483.1***
Rivera Smoothie 499.8
CCI/ Cyclesmiths 516.9
***Ness no longer uses a K&N so this number will be wrong. I always use a K&N on my bikes and cars.
Edit: Cryptoboy, Remember that this information is about 4 yrs. old. Ness may have gone back to using the K&N filter since then.
When did Ness stop using K&N? And are those numbers (for the Ness) for the Stage II version of the Big Sucker? I would think the Stage 1 version to have similar numbers to the HD SE air cleaner, as they are the same size.
Good info though Unome. I have the SE, that is a pretty drastic change between it and the stock air cleaner! I wouldn't have guess a 2 1/2 times the air flow between the two!