1997 Ford Thunderbird check engine light

I have been getting a check engine light,that started with the code of left bank running lean. I had changed the fuel filter a few thousand miles before,so I cleaned MAP sensor and reset the light. Soon I got another light indicating the samething so I changed the left upstream and downstream O2 sensors and reset the light. Soon got another light but the right bank was running lean. Changed the two sensor and reset the light. Soon gpt another light. Always get the light when pulling harder than usual or with more throttle.
Thanks for tour help.
Sorry but I didnt see about the money untill I scroled down but I am an old Korean war Air Force retired vet and dont have much money.