Hello all and looking for some advice.... Just picked up a low mile adult owned 02 wrx with 100k on it for my son and I to work on. Did the crawl around underneath and other than the COBB cat back it was sold and appears to be stock. Very good maint records and paper to support it. Like all used cars figured on some things to sort out. Torn boot on front axle (grease on exhaust smells bad) and it threw a cel of po136 rear o2 sensor. Reset it came back so I replaced it. Local auto parts store gave me a Bosch replacement, was feeling good and then a po420 came up. Now when I look at the two sensors side by side the tip that extends into the exhaust stream is different.
I have read the many threads on this but before I tear things apart did I introduce the po420 with the Bosch sensor? The upstream o2 sensor was replaced in August by a very reputable shop here in Portland. Not sure if there is a easy way to validate the codes.
I did get the official Subaru shop manual to help but am looking for advice, manual can't give you that!