Soot on sensor

I had multiple codes thrown in the last two months. Codes: P0171, P0171p, P1131, P1135.
I have changed the sensor, cleaned the mass airflow sensor, changed out a few questionable hoses, new filter, cleaned the throttle intake and air boot.
Ran super rough the next day over heated and threw the P1135 again. Took off the sensor and it was covered in soot. Put the original one back on to return it and get a new one. Turned on the truck and did nott make it out of the driveway. Now there is soot on both sensors.
I am wondering if I now need to take off the manifold and clean that or just replace the sensor? The throttle body was dirty but now it is clean. I am completely confused and thrown of what I should do next. But I am wondering how the soot is going from the throttle body to the sensor?