I'm really getting into autocrossing and I need to squeeze more power from my little d15b7. I'm looking for an inexpensive 4-2-1 header, a new cat, and muffler. I'm going to a muffler shop for the exhaust piping and cat install so I just need to buy the muffler. I'm looking at maybe a 5Zigen or Skunk2 muffler.