Headers on the v6 8g

So i just installed headers on my v6 a while back. They were like $125 on ebay (they were originally for the 2000 mit eclipse gt) anyways i had to remove a header bolt on each bank so it would fit... I noticed it doesnt have an egr tube port so i stuck a breather on my intake. I also noticed there arent any cats. My car has codes p0161 (bank 2 sensor 2). Is this because i dont have a pre cat on my header? I heard about using a spark plug non fouler on both postcat downstream 02 sensors but the sensor doesnt fit inside. So could anyone link me to a place where i can buy these 02 spacer things. preferably on ebay please