Well, the first question is why did you spend all that money swapping out all FOUR of them? Engine Management OBD codes tell you very specifically which one is causing your engine malfunction light to come on. With my ES330, the code showed Bank 1, Sensor 1. That was the one I changed. The sensors are located on both exhaust manifold pipes, one before the Catalytic Converter and one immediately after it, so one you can see in the engine bay, and the other is pretty much under your right heel. There should be no air blowing from the back unless a joint came apart.
Next consideration, Fuel/Air Sensors (before Cat) and O2 Sensors (after Cat) come in different qualities. The best and most reliable are Denso, which are the ones that were on there already as supplied by the factory.
https://www.clublexus.com/forums/gs-2nd-gen-1998-2005/816086-location-of-oxygen-sensor-bank-2-sensor-1-a.html
Denso
https://densoautoparts.com/
I have my own Scan Tool Module left attached permanently and read my own codes. You plug it in just above your left knee under the dash. You can also reset your Engine Malfunction light with it as well. When I got my code it was running lean, so the car was adding extra fuel to compensate. The Spark PLug was sooty, a sure sign of running rich. I replaced the Fuel Air Sensor and Reset the code. I got 100 yards and the light came on. I checked the code and it said it was running rich, adding less fuel to compensate. I reset the code, took the car for a run on the highway to burned out the carbon and soot, and the light has never come on again. For a 'Single Female Lost' it is a good investment.
https://get.fixdapp.com/home/1-0
So to summarise, it sounds like you have a faulty (no power), or even a loose (blowing air)sensor. Take it back to the shop.
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