There's been other posts regarding "opening up" the airbox (check old forums) & yes the cone part is an attempt at silencing the intake noise.
I sliced the cone off, left the rubber coupler connected (as a possible source for cooler air) & opened up the sides of the airbox for more airflow.
While some people on this board advocate a K&N drop in filter, I feel that a paper element eliminates the need for re-oiling periodically with no contamination of the MAF.
The only penalty for opening up the air cleaner is a more frequent replacement of the filter element. Difference in sound occurs only under acceleration. Normal driving is quiet (sleeper mode).
Seat-of-pants dyno indicates better response all around (Zetecs need all the help they can get!).
Cheers!
