I have a Bullet performance exhaust muffler. What will headers do for a D16? Also the exhaust pipe under the car. If I replace the cat what shoudl I replace it for and yet still pass smog? will it jsut make my car sound louder? Or will it help increase power?

 

Sounds like you could benefit by doing some reading and research. This is covered in depth every other day. I would start by looking here: https://honda-tech.com/zerosearch