If you drive your car on a road course, even a course without particularly high top speeds you will discover that the stock intercooler performs its duty well. Many complain that the aerodynamics of the vehicle are such that no air reaches the intercooler. Often these critics refer to a diagram Mazda produced that indicates pressure areas. This diagram was produced for the general public and not intended to have scientific merit. A road course will show you that air is directed into the hood scoop, as the intercooler is cool after successive laps. I know this from personal experience with my gently modified car. Dyno results on my S4 TII show 178rwhp or ~215hp (182hp stock). The dyno results were achieved with a muffler in place of the stock catalytic converter instead of a straight pipe that substantially increased power through the rev range, especially at low RPMs. (I would estimate the straight pipe produced 10hp and 20ftlbs higher, bringing the total to 225hp)
There are more conventional demonstrations as well. If you drive in the proper fog conditions you can simulate your own wind tunnel smoke flow testing and it is evident that air is directed into the scoop. Other similar situations are light rain, wet car after being washed and light snow. The scoop also increases the coefficient of drag TII by .01. (.29 Cd total) If air was not directed into the scoop Mazda could not produce this resulting number.
I am not going to argue the merits or disadvantages of an aftermarket FMIC (front mount intercooler), but I will argue that the stock TMIC (top mount intercooler) works in stock or gently modified conditions.