I decided to try this for fun and was very surprised with the results. I have a HP gauge in my aftermarket multi function display. I decided to compare a Short ram intake verses a fully modified air box.
First up the short ram this is in an automatic car (we didn't get the manual here in the US) second gear pull form 30-70mph 70 is where it shifts at WOT... 150hp
not too bad considering the engine is rated 130hp in this car here.
OK next is the modified air box same road same temp same day 159hp 9hp more and Intake temps were 30*f cooler
I guess this shows that air must be taken in from outside the engine bay.