Thank you for choosing JustAnswer and allowing me to help you resolve your Toyota questions!
When you say that you did a computer scan of the computer and everything shows as normal what you mean by that. Did you monitor the long and short fuel trim percentages? What are the numbers?
My mechanic and I did a test drive while he monitored the operation of the exhaust with his scanner and it showed normal operation. On my way home the Check Engine light came on. I returned to the garage and he read the code P0171. I don't know the details of his monitoring, but he said that it indicated normal operation whereas with the previous ECM it did not. I can get an answer to your question later today. It is 7:18 am here now.