Cochese is right, the air tube is on the passenger side for both. The collector appears to be 3 inch, as I measured it. The BBK is a 2.5 inch. I heard the car and it had no leaks. It seems that the ball socket from collector of header to x-pipe allows for the half inch difference in pipe size. It made it a little less expensive for me, so I did not replace my catback that is 2.5 inch.