Bump is there to create turbulance and reduce dust and particles going in. If you cut it open, you get real cool air going in, especially at high speeds.
But that causes 2 things:
1)Your intake sound increases (depending on your filter, it can multiply as the front plastic panel starts to act like a drum with air flowing through it).
2) You get more dirt in.
The second problem can be easily solved with more frequent cleaning. The first problem can only be solved by removing the plastic cover. That may help your performance but you will end up with an unbeliavably dirty engine bay in no time (if it rains where you live)