There seems to be some confusion lately as to the stages of modification and what should and shouldn't be modified. Here is a description of the stock pipe mod's and an illustration of the entire baffle assembly.

The illustrations go from stock directly to stage 3, with a suggestion as to how to make stage 3 louder if you want.

Totally gutting the pipes involves removing all of the chambers and isn't really worth it since the exaust nearly makes a direct exit once you get to stage 3. The other thing is that if you eliminate the entire baffle system it is like running the bike without a slip-on in place, meaning very little back pressure. That can cause performance problems.

So, here it is;

Stage 1 is simply drilling either 4 or 8 holes in the 1st baffle plate (directly behind the cone, which at this point is gone!).

Stage 2 is commonly known as reaching further into the baffle system with a longer drill bit and punching holes into the second/third baffle plate. (Maximum hassle, minimum effect...)

Stage 3 is removing the 1st baffle plate and the final exaust pipe, thereby eliminating the effect that the 1st and 2nd baffle chambers have on the flow of exaust.

Note in the illustrations that once you get to stage 3 you can drill additional holes in the 3rd baffle plate, but you risk loss of power due to the virtual elimination of the exaust's ability to create back-pressure. I would start with small holes, but understand that if the bike begins to run poorly, there's no going back.

Contrary to popular belief, there is no fiberglass packing in any of the baffles. The inside walls of the pipe are lined with fiberglass and that is held together with a perforated liner. It is best to leave that alone. Removing it does nothing more than create work, and the appearance of the pipe is much nicer with the liner in place. the insulation also helps keep the outside of the pipe cooler. Once the baffle system is defeated the fiberglass does very little to muffle the sound.