Its there and you can notice it when you pay attention. It should sound exactly the same on a fl and pre fl, ask Poeter since he has both cars. Ive been in many ep3s and they all sound the same unless the intake/exhaust is changed.

Gruppe m is pretty good as it has the water drain hole on the bottom. Even if water does get in, there is like a lump/basin on the bottom so it catches the water and wont hit the filter directly unless you drove your car into a pond.