This may be a stupid question, but who knows?! I need to change my O2 sensor(s) and was wondering if anyone had one or maybe two for sale. If so, what would one of you charge for that? Just trying to save some money if I can. Thanks.

Bosch makes them and you can get them from an auto parts store cheaper than from the Dealer. There are two "O2 sensors" and they are different. One is a "fast" fuel ratio sensor, up front, and the other is a "slow" O2 sensor. You need to know which you need. They look the same except for the connectors are different.

I replaced both of mine and they still trip a code off road because they don't heat fast/strong enough. The one from the Dealer was $350 and a parts store was $160.

www.sparkplugs.com carry Densos.

are you sure you need O2 sensors? a few years ago i thought the same thing and a throttle body cleaning did it for me. just throwing it out there.

Also, along with the MAF cleaning, try cleaning the front AF sensor with something like non-residue brake cleaner or carb/throttle-body cleaner. My SC'd 4Runner was acting up when under acceleration. It was not smooth and sometimes had dead spots and loss of power just starting off from a dead stop. I just cleaned the front AF ratio sensor and now it made a world of difference. The sensor was very dirty with quite a bit of exhaust crap on it. After cleaning it and letting it dry, then re-installing it, it makes the world of diference. Much smoother acceleration now. I had already replaced the MAF sensor and TPS a few months ago so I pretty much figured they were not suspect at this time. Did not touch the O2 Sensor behind the cat. No codes were shoing up for the front AF ration sensor but I could see the readings were very irratic which told me the sensor had issues. Cleaning definitely helped.

The perm fix is URD's fuel upgrade kit to take care of all the SC'd 4Runners woes but that is coming once I get my piggy bank restocked here after bonus time next month.

Ricochet

You mentioned a 'throttle body cleaning'. What exactly is that, and is it something that can be done at home or is it a maintenance shop thing only? Thanks.

When you say the front AF sensor, you mean the front O2 sensor right? And when you cleaned it, did you use a brush or just a cloth? I haven't even looked at my MAF sensor yet, based on the error codes I posted before, I was told it wasn't my MAF. Here's all my symptoms:
-Real sluggish reaction...no get up and go.
-Check engine light with these codes: P0171, P0125 and P0135
Anything else to look at? Thanks.

Check the Toyota section here for the t'body cleaning (link above). If that thing has a 3.4 in it, there's a link for an FSM sticky'd over in the T100 section that can get you in the ballpark.