1997 pontiac grand prix code 121

yes, my 97 pontiac grand prix has been coding out the code 121 i replaced mass flow sensor and still problems. before i replaced it would hesitate and stall at times. i also cleaned the throttle body with cleaner before replacing sensor and since then the car when starting up engine will fluctuate, when putting on a/c. the engine wil run fine after driving,when turn off and restart after a few hours it wil again start to flucatate. my question is could the throttle body position sensor be bad?

P0121 Throttle Position Sensor/Switch A Circuit Range/Performance Problem

a P0121 is a problem with the throttle position sensor not the MAF, so to answer your question yes, the TPS is most likely your cause.