they sell a special notched deep socket to remove the damn thing. I bought a 22MM, maybe 24MM combination wrench at like harbor freight for 10 bucks and cut it in half. If you pry down on the exhaust with a 2x4 you can gain a little room. Then disconncet the o2 sensor connector and feed the box end of the wrench down the wire until you get to the hex of the sensor. I then slid another wrench ,box end, over the sawed off piece making the wrench effectively a 90 degree tool. The sensor came loose very easily and I was able to back it out by hand. Same in reverse for install.