This is my take on the doors. There made to let air in and not out. So I thought why would you not want to let air out. Then I thought what kind of weather to you encounter in Germany, and all the surrounding countries. Its gets to below freezing conditions, in a great portion of the European countries for more then 6 months at a time. So I figured they did that so the car would take air in while it was in motion, exhausting more heat. Then when the car is stopped it could keep that air in there so it can maintain a consistent air temp, in the attempts to lesson the chances of explanation and contraction that the metal, and rubber pieces would do. They pretty much don't want the belts, hoses, or like the engine block to crack.
That type of engineering won't work in places were the weather will exceed like 90 degrees for any length of time. You'll kill that engine a lot faster by keeping that hot air trapped in there.
I had personally taken mine out of there, and noticed a difference in performance, because well for one it allowed more external air to be channeled into my cone filters which is a good thing. And I noticed that the engine would just rev out so much, as when it is to hot. Has anyone noticed that the cars power will drop a touch when it is a really warm day. I live in the Greater Los Angeles Area, and warm to me is like 90. I've noticed a difference when it is cooler then that. I think these engine setups are able to put out a lot more, if they were just properly set up for warmer climates.