Porting Stock Header:

 

Want to make your stock header flow a little better? Read this

You'll notice the large weld inside it. (see pic)

Get out your dremel with sanding wheel.

Now slowly sand/grind away the weld, leaving some weld there, but remove enough to increase the exhaust flow (see pic)

After that is done, continue smoothing it out....

I have been riding my bike like this for a few months now with this mod and did not have any problems with the weld coming apart. It deffinitely adds some power, especially if you cut the screen/baffle out of the exhaust and remove the spark arrester.