Remove the vibration damper that's in the way of the forward post cat sensor to replace and def use OEM, I've tried the knock offs they do not last. 250/4 is a good deal. I think about $65 @ is the best I've paid.

I usually cut the wire and use a deep socket to get them out vs. an O₂ socket but i recently saw a trick of putting a hose clamp on the O₂ socket to keep it from spreading and that's a great tip.

Some of my O₂ sockets are offset and that helps in two ways:

1) you can hit with a hammer.
2) you can turn it from the back side.

For the forward post cat sensor i think it was, i put the offset O₂ socket on and put the 6" wobble extension in from the bottom, then i can use my high torque impact to turn clockwise to break it loose.

Recently helping brother we needed to use a long breaker bar and our legs to remove a cross threaded O₂ sensor so good luck you don't have any of those.

__________________
2011 E70 • N55 (me)
2012 E70 • N63 (wife)