Had K&N 57i (mean dia 4.25", length 7" -> surface area 93 sq ins), then after changing the intake pipe tried a Ramair foam filter which was bigger (dia 7", length 5" -> surface area 110 sq ins).
With the Ramair, the AFR was showing blue all the time (very rich) and using a wide band lamda read .83-.88 at steady speed taken at 3K/4K/5K/6K - again very rich.
Back to the cone 57i, I now get the occasional green/yellow showing on my afr. (I always get red (lean) on lift off).

So my non scientific comparison indicates that the added surface area of the concertina shape on the cone filter flows more air through than a seemingly bigger area foam.

Obvious really, but you have to try these things to make sure !!
Roll on 10th May for the remap ! :D
Stan