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If measuring CFM on a flow bench, It makes one whale of a difference how much vacuum is used to get readings. When I worked in this business about 35 years ago there was no standard among head shops nor was there any standard for manufacturers. Hopefully it is more uniform now, I really don't know. Also it is possible to get better than 100% efficiency but only at a narrow RPM range. its all about getting valve overlap (cam profile) in sync with tune length to produce the greatest air velocity with the straightest and smallest port opening and high attack angle at the underside of the valve. That is why most cars have variable length and volume intake manifolds now with 5-6-7 or 8 speed transmissions now.