While they may improve performance, it is very unlikely they will improve
gas mileage. If they improve max performance, and you take advantage of the
extra performance, you may actually decrease fuel economy. Given the CAFE
rules, don't you think Ford / GM / Toyota would have include this sort of
intake if it would increase fuel economy by a measurable amount? It is
unreasonable to think they are spending billions on 6 speed transmissions,
new engine designs, low rolling resistance tires, etc., etc. but they won't
install a simple air intake system that would increase fuel economy.

Ed

While I personally agree with what Ed says in his reply, you will probably
get as many varying opinions about the benefits of/ harm caused by CAIs as
you will asking the question of "Which is better for my vehicle- the
recommended oil, or what I want to use?"
I leave my vehicles relatively stock, and have always gotten at or above
what the sticker says I should get MPG-wise. I don't drive like the old fart
that I am, nor do I hot rod them.
IMHAWO, it's up to you to decide if you think from the research that the
initial cost of an add-on will pay for itself in savings over XX period of
time.

SC Tom