New mod i added!
 

Once you get ur custom muffler it will look good now u have to make it sound good! get a peice of paper, cardboard, Poster board or whatever (experiment see what sounds good) now cut a piece shaped like this ...

___
___|tab |
|_______|


Might have to shape it a bit different depending on ur set ups.
now fold the tab and glue/tap it to your motor for that muffler rattle effect!