Today I was trying to figure out which K&N filter to use with the space limitations of my SLC. I went to K&N Universal Air Filter, Crankcase Vent Filter, Flame Arrestor, and Filter Wrap Search by Dimension and picked out a couple of filters. I sent an email to K&N '[email protected]' with the filter numbers and my engine type and size and asked for the CFM of the filters. The tech got back to me in 30 minutes with the filter CFM and my engine CFM @ 7000 rpm. Great company!