Just bought a 2001 WS6. Have been an enthusiast for years. It seems as if there was a lot of restriction when i opened my air box. The plastic on the bottom (right under the filter) i cut most of it away. Felt a small increase in response. I also saw this large thin piece of plastic seemingly covering the radiator. It also seems to be sestricting a lot of airflow. I was wondering if it is safe to completely remove the piece. Not sure what it's purpose is, if any.

 

There have been a few threads on this very subject. I can't remember the exact links, but they should turn up by doing a search.