2007 RAV4 ECU code P0171

I have a 2007 RAV4 4wd, I bought in October 2023, after almost a week of having it I noticed a shutter. Thought it was just the surface of the road. I finally had a mechanic test driving it when it happened. They said the torque converter and best to change transmission and out new torque converter. Had a second mechanic do the same and they said the same thing. The transmission was replaced with one with 78k miles and new torque converter out in it. The shutter started again shortly after getting it back. Then they thought maybe other issues, months later and thousands of dollars later, it is still happening. Also had dash lights coming on and changed a bunch of parts for the lights to only come on again. The shuttering only happens when it’s in drive, if you put it in 3 it doesn’t happen. I saw a video where they said you have to have a software update after replacing transmission and torque converter or it will start happening again. Is this fix you are showing on this video something that would fix these issues and do you do this for 2007 4wd model parts as well? The code showing when the dash lights come back on now is only showing P0171 after changing several parts. My mechanic talk to a guy from Toyota and the said it might need a new computer and that may be causing the lights to come on. My mechanic said he needs to flash the computer? What do you think?