Ya not sure you were able to get the O2 sensor out yet, but i just did my DP last week and i was able to get it off with just a cresent wrench. though i did it a bit differently and disconnected the stock DP first from the engine area and the cat back. Then i disconnected the O2 sensor. (there are 2 little plastec pieces that hold it in line under the heat sheild you'll have to pop out, then if you gently pull on the wire you should get enought slack to disconnect the O2 terminal). With the DP out and the o2 sensor disconnected, its so much easier to unscrew the actual sensor from the pipe.