for psychological reasons a loud aftermarket air intake can slightly improve fuel economy by causing the driver to slow down

this the the opposite effect to how a very quiet vehicle can cause you to drive 10 or 15 miles per hour faster

do not underestimate how complex air flow is in the intake

the air DOES NOT flow like you imagine water flows

the flow in an intake behaves closer to the gases in a submachine g%n

Aftermarket intakes should be tested against new filters in the original factory intakes, then tested a second time at approximately 10,000 miles of use

there is very questionable behavior when magazines test aftermarket intakes,
especially when money changes hands for advertising in the magazines,
for reprints of the test article bought by the cai manufacturer,
and also when "rent" is paid for the vehicle used in the test

have "significant" air intake designs been created?

yes, they have names like
"water/alcohol injection" and
"turbocharger"