From everything that I have read.... Don't get rid of the stock airbox. Rotary valve rotax's like to "see" a little bit of induction restriction. If you run pods, you will have to jet it way up, and it turns the sled into a finicky pain in the butt. It will have louder induction noise, and will burn more gas, but will not necessarily increase performance enough to warrant doing this.
I've owned and modded several 670's with twin pipes, heads, big carbs, etc etc. , and I have never removed or modified the stock airbox.
