I think after just doing mine that they want you to buy two sets and that is probably the best way to do it. Now, what I did is cut the plastic keys off of the O2 sensors connector so that the extension will mate up to plug for the o2 sensor and it plugged into the cars harness fine. The back sensors are supposed to be turned off in the tune because of the O/R H pipe so I just screwed them into the H pipe and did not connect them because they obviously wouldnt reach each other without another set of extensions. But i dont see the point if they are not turned on. We used to screw a spark plug into our foxes and just bust off the ceramic with a hammer and it sealed the bung just fine. I dont see why that wouldnt work for these cars I just used the stock sensors because I had them. If on the other hand I find out even though they are turned off that they have to be plugged in then I will just splice them together with the same size wire and save some dough for my cams which was my next mod im after. Hope that helps.