Hey,
Just got done drilling my exhaust pipe and took it for a quick ride. I definetly notice a difference in the lower rpms but not so much above 5k or so. I just have 4 1/4 inch holes so far. Would increasing the size or number of these make a favorable/big difference?

Thanks,
Ben

Try using the same holes, but go to 5/16".  If that is not good enough, bump it up to 3/8".  Go in stages.  Too much and you can't go back.

You can always get some big sheet metal screws, or plug the holes with some sheet metal and JB Weld. No big deal.

Just be prepared to jet.

I wasn't aware that drilling required rejetting... I thought you were just modifying the baffle instead of the actual exhaust.

Mufflers are just a can with baffles, and sometimes some perf sheet or packing. When you drill hole in the baffles, you are changing th back pressure in the exhaust system. Less back pressure will mean the engine breathes more air.

A few small holes on the rear baffle doesn't make much of a difference. The only problem is, the GS is jetted pretty lean in the US to start with, so it is possble even this small change may lean it out too much. I wouldn't worry about it a lot though.

I drilled two 1/2" holes and I really like the sound.  I stayed with two because I was afraid I wouldn't like it.  I do though, it's way cool.

Ok since I don't feel like rejetting at the moment i'll just leave the holes at the size they are. It doesn't seem to be running any leaner than before. Now it's time to whack off that fender.....

Okay, dumb question...
Where exactly are you drilling the pipe? This I do not know. Can someone please run through the procedure so morons like me can figure it out?
I just dont get where you are puting these holes. I want some in mine!

http://www.bikepower.net/

Look in the menu to the left of the screen.  "Modification Manuals", then click on "Engine Modifications".  There are detailed instructions with photos and diagrams.  

Just remember.  Start small and listen to the exhaust tone.  Then go bigger if you want to.  Don't start whacking huge holes in it to start.

I was also confused about this at first. There are basically 2 rings on the back of the pipe. I drilled on the inside of the outside ring but outside of the inner ring. There's a flat area in there that's about a milimeter thick...