Cranbery

So I replaced my TPS with a new out of the box one after using a used one from a member here and both were calibrated properly with an OPDII. After calibrating the TPS it ran perfect and then somehow lost the calibration? Calibrated it again and it lost it again. It still puts my car in the safe mode where it won't go past 2k rpms. However the only codes that come up are for the sensor. Could it be that the new in new in box sensor came bad? Or would it make sense that the ECU is bad and that's why it doesn't remember the calibration and falls from the 14.5 it should be at to ~10. It falls in and out of this safe mode throughout the day sometimes drives normal no engine light sometimes normal with the engine light. My mechanic said it could be that the throttle body is bad but Im leaning towards the ECU. Neither the throttle body nor the ECU come up with malfunction codes. Thanks. 99 sc300 vvt-i no engine mods, 132k miles.