You say that both O2 sensors are not functioning. What are they doing when not functioning? Flatlining at 450mv? You may be having a ground issue depending on what type of harness you are using, whether the sensors are case grounded or isolated grounded. Here https://www.lt1swap.com/vortec_o2_sensors.htm is some info about that. I'm thinking that they may be losing ground somehow when you are slamming on the brakes. I know it's far fetched, but may give you something to check out.
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