P0171+P2195 lean on bank1 only

Hi Guys, First post here.

Here is my situation:
I purchased a second hand 2007 Tundra double cab long bed not too long ago but I did not drive it much.

It developed a problem with the secondary air injection pump, with P2440 code, bank 1 switching valve stuck open. After searching various Toyota forums, I DIY'ed a bypass kit using a regular automotive relay + 4.7k ohm resistor and some wires, and I also put in a bypass plate sandwiched between the switching valve and exhaust pipe.

The P2440 code went away! But I now get P2195+P0171 codes. I don't think I got these 2 codes before the bypass, but I did not drive the truck long to be really 100% for sure.

But in any case, regarding the P0171 and P2195 codes, here are my observations:
1. My LTFT and STFT for bank 1 are: ~30% and ~20% respectively,
2. LTFT and STFT for bank 2 are perfect, change between 0 and ~3%.

So **I think**, maybe my MAF and fuel system are good? Otherwise both banks will be lean, and I would get P0174 code?

I initially thought there is an exhaust leak on bank 1, due to the fact I took apart the SAIS switching valve on bank1, and I honestly did not see a gasket between the valve outlet flange and exhaust pipe flange, so I put on some Permatex Red High-Temperature RTV Gasket Maker between the switching valve flange and pipe flange and tightened them up good.

But after that, I still get P0171 and P2195 codes after 1 hour drive.

I then used Car Scanner app on my Android phone + ELM327 dongle to log AFR O2 voltages on B1S1 and B2S1, and during engine idling, I pressed the brake pedal to simulate a lean condition (this idea is from several Youtube videos).

My O2S5 voltage (Oxygen sensor 5 Wide Range Voltage, I don't know why the software shows sensor 5 voltage instead of sensor 2, but I assume this is the B2S1 AFR sensor, as other sensors are disabled in the software) consistently hovers over ~3.25v during idle, and goes up to 3.4V when I pressed the brake pedal, then goes down to ~3.1V when I release the brake pedal, then it will go back to ~3.25v after it "stabilizes" for several seconds.

My O2S1 voltage (Oxygen Sensor 1 Wide Range Voltage) however consistently hovers over 4.5V during idling, and it shoots up to ~5V after I press the brake pedal, it probably went over 5V as the software recorded a flat line at 5V for several seconds. Then the voltage drops to 4.5V, but it never went below 4.5V (like B2S1 does under 3.25v) and its response seems slower compared to B2S1.

I think my O2S5 (or B2S1) is behaving normal. But my O2S1 (B1S1) is not.

Are there other tests I can do to positively determine the problem is the bad B1S1? As I don't want to spend $180 dollars to replace a non broken AFR sensor.

I am thinking to swap the two AFR sensors from 2 banks, and observe the voltages and potentially trigger a P0174 code? If I get a P0174 after swapping the sensors, then I can positively identify the current B1S1 is broken?

What do you think?

Thanks!

Hexar