WHen the engine is cold you will feel a huge gain.
But once it gets hot under there ,forget about it ( and the ES 300 engine bay is one of the hottest under hood temps around ,due to its lack of air cuiculation)
all the power gains are lost and even then go well below the out put with the stock box.
A short arm is a rice part with zero real world gains.
Just try a good dyno to see the differences or gains and losses which is how i gauge all my mods for effect. As the brain has a tendency to alter perceived gains with the endorfins of a new toy. Kind of why there is usually never bad s*x
(- teeth ,whips and chains, i don;t do or need that)
Look at the Lexus sc 300/ soarer /supra guys with the inline 6 .NO company has made a better intake than the stock airbox with a bfi upgrade! NOT ONE! And all it is ,is basically cutting a hole and removing the ballast from the air box.
It is basic physics
short arm =Hot engine bay air =expanded =less oxygen molecules=more unburnt fuel=wasted gas and performance
cold air intake =smaller volume of air =more oxygen molecules to feed the combustion process= hotter burn temps= better afr =less fuel for a complet burn of fuel= as well as better emmisions also.