header side it is a 2 bolt flange and the piping leading from the exhaust system is a 3 bolt, the gap in between is what im guessing is supposed to be the cat. but the thing is, on the stock piping that i took off the car, it was all a one piece pipe. so i have that 12'' gap, where i think the cats supposed to go? im like 99% sure theres supposed to be a cat, i just wanted to make sure i wanted to get the right cat. thanks