Thrust issues with AFR gauge and Brawler carb

Here are a few thoughts and suggestions that may or may not help. I'm assuming the o2 reads normal except at wide open throttle.

1. Try another carb and see if you get the same results.
2. Move the sensor to the other side of the motor to see if it reads the same.

Fuel distribution is not always the same for each cylinder in an engine. This is especially true with dual plane manifolds. Also not all cylinders respond the same to a jet change.

On my dyno I have an o2 sensor for each bank.
Remember that the o2 reading is an average of the 4 cylinders on that bank of the engine. One or more cylinders could be rich, lean or any combination. The same is true when looking at each bank of cylinders. One side can be rich and the other lean. Looking at sparkplugs helps but can also mislead you. Same with egts.

If it has headers, placing the o2 sensor too close to the collector can cause the sensor to be biased to a particular cylinder.

3. Try as as an experiment a main air bleed change.

I have found that sometimes when a motor doesn't respond to a jet changes that changing the main air bleed will move the air fuel ratio.