i have a 97 honda civic dx hatch back. i use to have a b18b1 motor with a dc header. the dc sports header doesnt have a o2 sensor tho, but on the cat it haves two. so when i did the swap to a b16a the stock header has an o2 sensor too. so now i have three to plug in. i dont know which two is the right one to plug in.. one is on the stock header, and two is the cat.