Do you need one or two defoulers for the o2 sensor is down or upstream ?I got my catted 1320 downpipe installed this weekend. It wasn't fun. It took forever, I kept getting snagged on dumb ****, and the car beat me up a bunch.. but I got it, and the fitment was good. I used the Vibrant J defouler with the medium insert and no CEL so far. The only step in this process that went smoothly really was the Vband came off without a problem. I had to bolt the stock DP to an engine stand to get the O2 sensors off. Now I think I need to hit up JST.