UGGGHHHHH!!!! I bought a new upstream O2 sensor for the 2.4L... It's time for a new one. While I am in there I am going to soak the CAT with a foaming DPF/CAT cleaner. Tore into it today and wouldn't you know it, the O2 sensor will not budge. SO, on my next day off I am heading to the storage unit where my tools are, busting out my cordless 1/2" impact and I am going to get that prick out. I used heat and a breaker bar. The sensor is oriented vertically so it is not hard to get to and it is directly mounted into the top of the cat. The downstream was cake. Smooth out, smooth in.