The carbonio has a K+n filter on which gives it a nice growl and when coming off accelerator or changing changing gear will give you a nice whoosh noise! However get it remapped and turn up the boost and that whoosh becomes a very loud and pedestrian scary whoosh!
I have found that it doesn't make as nice noise as my old fiesta zetec-s with a pipercross on, but it does sound nice,maybe even like a scooby growl[

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It defiantley lets the car breath better,it wont give great gains in torque/bhp if at all but it pics up better especially on a nice cool evening/morning