LR3 O2 sensor recommendations
 

I assume like most cars, the upstream are for AF ratios and the downstream measure the cat operation. If so, I plan to just replace upstream. I realize there is some year specific stuff with these plugs. Besides that, is there any recommendations on brand? I tend to go Bosch for sensors. But if anyone has some input, I would love to hear it. Im about 120k miles and I dont think they have ever been changed.

I changed mine out at 162k miles due to error codes. The originals were Denso, which is what I replaced them with. I did both the upstream and the downstream. The downstream are much easier to access. I have an 05, and the upstream ones were identical (Denso 234-9075), but the downstream ones were two different part numbers (Denso 234-4265 and Denso 234-4266).

Going to give Walker Products a try. Rumor has it they are Denso re-packaged. They certainly look identical in every way. Also they were on closeout at $60 each. If they are no good, I may just get some actual Denso ones. New spark plugs on the way also. I have lots to do once it get warmer out!!

update: So far no issues with the Walker sensors. New spark plugs installed too. Had some lean codes after. New plugs/sensors may have been better at their jobs than the old ones. Reset adaptation, still had a code. The codes would take days to show though, it was not really bad. Well based on another thread, I decided to seal my throttle body gasket and EGR gaskets with Reinzol high-temp sealant. I think I reset adaptations one more time after and now for weeks all is well.