Impreza STi with roller barrel throttle bodies

[Svensson]

Turbomanifolds were not connected in this vid as you can see:

http://www.motorworld.net/forum/images/icons/icon2.gif http://youtube.com/watch?v=ta6iJiKbfHg

[dannyroz]

Instant throttle response...

It would be cool what a true NA boxer motor would act like

[Svensson]

Sorry for the noob question, but what exactly do they do?
They can be compared to Individual Throttle Bodies, or any other induction system that offers a separate throttle body for each cylinder, instead of one big throttle body feading all cylinders. Like dannyroz said, one of the biggest advantages is more instant throttle response and the potential to get more air into each cylinder, because each cylinder has its own supply of fresh air and fuel. Basically an individual throttle system is the ultimate in induction.

Another big advantage (at least to me) is the glorious induction growl they help produce. It just sounds so racy. Think BMW M3 (CSL), McLaren F1, motorbikes, racing cars and many more highly tuned engines. Anyone can put a big exhaust on their car and wake the whole neighbourhood, but to that with your induction sound alone, you'll need an individual throttle system :-P

For more info on ITB's read this: http://www.autospeed.com/cms/A_3049/article.html

Some nice ITB soundclips:
http://youtube.com/watch?v=S5bsMRFOvXg
http://youtube.com/watch?v=gfNZFurebtE
http://youtube.com/watch?v=DVS3CI-9C4E