I've had a recurring P0430 code which I assumed was just due to my car not having cats but perhaps my car was trying to warn me about the sensor.
Just wondering. You are aware that the P0430 applies to the REAR O2 sensor(s) while the P0171 and P0174 apply to the FRONT O2 sensors? As a further reminder that only the front O2 sensors affect HOW the motor runs. The rear O2 sensors are just to monitor the cats. As such do not affect how the motor runs.
Let me give you some food for thought. I'm a big believer in Occam's Razor. The lean DTC affects both banks right? Therefore it's more likely that what ever the cause is it should also affect both banks. What that means is for the lean code to be a "bad O2" sensor it means that BOTH front O2 sensors must be bad. Think about it. Which is more likely? Two bad O2 sensors or a single common fault that affects both banks? Not to say that it's not possible for you to have two bad O2 sensors but Occam's Razor says that it's more likely to be something else.
Or at the very least, rule out the most likely causes before trying something that is less likely.
Occam's razor
en.wikipedia.org
To others looking at this thread. This could be an interesting case study in how it's possible to start well intention trouble shooting by changing parts only to end up at a professional mechanic's shop. IE, start trying parts without a fix. Get frustrated. Go to a professional thus throwing away all of your effort expended before hand.
I didn't get the fuel trim numbers exactly but they definitely improved when I brought it up to 2500 RPMS
Regarding a POSSIBLE common cause that can affect both banks a possible answer is hiding in plan sight. What is one symptom of a vacuum leak? As RPM's go up, the intake vacuum goes down. This causes less un-metered air to be drawn in. This causes fuel trims to go from high positive values (adding fuel) to adding less fuel at higher RPM's.
I have a propane wand that i use for this sort of work. Again if this were my car, I would test the O2 sensors by adding an external fuel into the intake while monitoring the front O2 sensors. This will either PROVE the O2 sensors work or not. Once you KNOW that the O2 sensors work, the trouble shooting can focus elsewhere.
In my case, I would then use the propane wand around the engine bay while monitoring the O2 sensors. When the propane is near the vacuum leak point, this will show up in the O2 sensors by a rapid switch lean to rich. At this point you will KNOW that a vacuum leak is the CAUSE of the problem. Further you will know where the leak is located.
Brake clean can be used instead of propane. Just need to be much more careful to avoid a risk of fire.
Now if your goal is to avoid paying a professional to fix your car and it gives you piece of mind to change the O2 sensors just to be sure that you are dealing with known goods, then by all means, go for it. After all, in the end, even with changing out a few good parts it's likely cheaper than paying a professional mechanic. However if at the end of your work the car still ends up at the shop, all your effort will be wasted and only beneficiary will be the mechanic (if at all).