Brian brings up an EXCELLENT point.
The gain you will see will be determined greatly by how well the original filter is sized to the engine. In the case of a properly sized filter there will be negligible or no gain.
In the case of my Vette, the filter area and mass air flow size are undersized for the car. The injection system and associated components were originally developed for a 305. Then before production, GM brought back the 350, so they simply stuck the 350 under the same system which was probably marginally sized even for the 305.
My C240 has less than half the engine displacement than the Vette and it has a mass air flow sensor that is at least twice the size of the one on the Vette. One of the air filters on the C240 is probably as big as the single air filter on the Vette. The MB has twice the filter and mass air flow area but only half the displacement. Adding the K&N on it, or even taking out the filter element all together would probably not increase the flow.
Brian, "you're the man!"
Have a great day,