That is so not true. The only difference between putting a CAI on a 4 cylinder to putting it on a 4.0 or even a v8 is the fact that the driver themself wont feel the difference as much as they would with the 4 cylinder. But just because the difference isnt as noticeable doesnt mean its not there. There have been MANY reputable companies/people to test and dyno the differences a CAI makes in both power and fuel efficiency and on most vehicles the results are concurrent (yet not always as high) as what alot of companies claim for gains on a CAI.

And also, most of those running a WAI are driving old tiny geo metros that are underpowered as it is, and get well over 30-35mpg easy. A WAI on a large engine would be counterproductive, as enclosing the engine bay and raising engine temps would require mods to the cooling system to keep the engine properly cooled. The risk just outweighs the gains by too much.

 

What we need to so is get someone to goto a shop with a dyno. And do a few runs

First stock airbox with a paper filter
Second. Stock airbox with K&N drop in filter
Third. CAI

#'s don't lie