I've done several O2 sensors. In my experience the crow's foot type O2 sensor tool ($10ish) is what you need for the low clearances on a soob. The socket type is just too long. Soak it (cold) the night before you try to remove it. Good luck.

Well it's here and the rain has let up.. I think I'm going to try it now.

 

 

All done! Kroil is the best stuff!

So I came back from a drive and guess what.. it's still doing it! I'm glad I still changed it.

 

Anyways so I ran torque on the phone to look at the timing when it happens and it seems (still need to check) the timing seems to dip as low or almost to 0 degrees.. I would of had a screen shot but I guess the phone froze since I had it set to do 5000 datapoints

 

However the next one I will do will be the timing. O2 sensor and engine rpm.

 

And now that I said that I know endwrench had some thing about how some legacys, impreza in the 97-99 model years that had some bad programming on the ECU which made the ECU think it was sensing knock when it really was not.