Tons of PB blaster, heat, and pounding on a 3/4" breaker bar with a 5 lb. hammer. I tried the 1/2" bar but it broke The special o2 sensor attachment is a must have too, I rounded off my passenger side sensor pretty good until I found one of those. Also, if the sensor is bad anyways, try hitting the area where it threads into with a punch, it may help jar loose some of the nasty corroded gunk that's locking it in. Welcome to one of the least fun things to do to a Vehicross.