Louder Exhaust?

If you want louder, just switch to a drag pipe, it'll also give you more top end. If you notice drag pipes really don't have silencer's but more a typical straight pipe.

Other than that, unless you can custom make a pipe, extending from where the head pipe meets the silencer.
 
I have the Fatty and Power Core II on my blaster and every one says it's just as loud as the other bigger quads, but it's on a high compression 248cc engine, put some compression in it and it'll get loud.