Gutting the airbox refers to removing the shelf and horns
from inside. This is a one piece unit that is cliped and glued
in the airbox.
The power breather is about $100.00 and I can't see
it working that much better to justify the cost.
I personaly removed the entire airbox and went with K&N
filters. (About $180.00 for my triple 6).
That seemed to work the best for my set up. The biggest
improvement was that I now have a ton of room under the
hood to access my carbs, cables, pumps etc.
Regardless of what set up you go with you will have to
adjust your jetting as needed. (usually 1-2 main jets taller)
Just my 2cents