Plz help, o2 sensors, now p0440

Hi, I inherited this 2002 tundra v6 from my dad. The check engine light was on when I got it, throwing 02 sensor codes (both banks) I replaced them, the light went off but I started noticing "surging" after about 5 minutes of idle, and also noticeable when in lower gears driving. My wife said she thought it was gonna die at a stop light the other day. Today, it was raining, I was driving around and check engine light comes on, this time p0440 AND p0136(o2 sensor). The o2 sensor was visually loose with gaps between it and the exhaust (whoops) so I fixed that, but it still surges.. Any ideas are appreciated thanks!

I have noted that along with surging, it has low power and not as responsive as I think it should be.

 

Questions:
Which brand of O2 sensor did you buy, and where did you buy them from?
To clarify, you replaced all four, or only two on one side, or one on each side, both rears, both fronts, one front, one rear?

Other members have found these trucks to be finicky about brand of sensors, scAmazon and fleaBay are chock full of counterfeit automotive parts, and many would recommend replacing front and rear sensor at same time.

P0440can be as stupid simple as you didn't click your gas cap down all the way.

 

Actually, more questions:

What were the original codes being tossed?

Did you check to make sure your connectors were secured and you didn't nick any wires? (asking b/c P0136 is circuit/voltage related)