When the Bosch O2 sensor failed on my AEM unit,, it would go to full lean immediately after its warm up cycle.
My failed sensor did not have a lot of use on it. I called the AEM Tech line and they had me do the ‘Gas Rag Test’ to confirm that I had a failed sensor. Prior to spending the $$ on new parts you may want to call the AEM Tech line and get their input to resolving if you have a sensor or gauge issue.
