Question about b pipes

Well....I had saved enough money to purchase the stillen lt headers and jba catback exhaust. My question is about the b pipes. I noticed that those who have the stillen headers have installed high flow cats on the b pipes. Where do you place the o2 sensors? I noticed that the headers have holes for the o2 sensors...is that where the stock o2 sensors go? Do I also need to place o2 sensors on the b pipes. I have been a fan of the Banks exhaust due to the sound, but the performance gain is just not there. Soon to be a another member of the stillen lt headers and JBA exhaust club.:cheers: