Gonna put headers and new CAT on my Si, to go with HKS, Apex-i exhaust and short ram filter. Don't know if I can pass a smog with the high flow CAT. They're crazy inexpensive on ebay. Around $30 WITH shipping?!? I don't know what's up with them. Any advice? Do they give you more HP? bottom end? Top end? I'm going from a Chevy Small Block 406 to the Civic Si. I'd rather put things on the car that give low end torque as supposed to a top end boost. The car is just to fun to leave stock.


Thanks!