That porthole is strictly a resonator. It creates a whistle effect that cancels out the audible frequency of the air that's rushing in the air box and airhat. You can shave that and cap up that porthole as long as you can make it airtight. It would essentially be the same as the k&n tube only kit. There are actually 2 portholes, or resonators, in that air hat. The other is closer to the throttle body.