By the time you buy another header pipe and get the $40 Ebay Muffler it may cost you just as much or more than the $99 ebay CRF230 exhaust. If the stock muffler is made like the Hawk muffler all you need to do is drill a few large holes in the end plate in the muffler. You will then have strait through exhaust. I posted a picture somewhere on here.
Edit: Here's a picture before I cleaned it up with my rotary tool.
