2001 Nissan Sentra Catalytic converter

Hi
I have a problem when I go up a steep hill. My transmission slips to a lower gear.

I went to a transmission shop and they said the trans was fine. When they test drove it, he took it to a muffler shop. They said it was the Catalytic Converter.

I took it to a dealer, they said the Catalitic conerter was fine. They did further checking and it was the Massive air flow senser.

I checked to see what the massive air fow senser does. It is an oxygen mix senser.

My car runs find and the engine does not miss. When in the situation of going up steep hills, giving the car less gas it returns to normal.

Could the Cataytic Converter have caused the senser to fail?

Thanks,

Jim