P2100 Throttle Actuator Control Motor car won't accelerate normally

Gonna try to condense this as best I can although it's a bit lengthy

2008 Mitsubishi Galant ES

6 Months ago my car out of the blue while driving, the service engine light came on and the car would not accelerate past 2k RPM no matter how you pressed the gas pedal. I took it to the dealership for a diag and they told me that there was a "loose pin in the wiring harness" which they fixed. They charged me $250 for the diag and fixing the pin. Car worked fine

3 months later it started doing the exact same thing. I took it back to dealership and they confirmed that this was caused by the code P2100 Throttle Actuator Control Motor. I bought a used throttle body assembly and replaced myself. It worked for about a month and started doing the same thing. Dealership agreed to do another diag for free and came back and said they attempted to control the throttle control motor using their equipment and it was malfunctioning. They offered to sell me a brand new one for $900 which I was unable to do. I did a warranty exchange on the used throttle body and after replacing it it's doing the exact same thing.

Dealership is saying the problem is persisting because I need to buy a throttle body from them new and that until I do that they are unable to locate another source of the issue. Took it to autozone and they are corrently confirming the following codes

1 P2100 Throttle Actuator Control Module
2. P0638 Same
3. P0102 Air Flow Circuit Low Input
4 P0113 IAT Sensor High Input

Please assist if you can. I've always been cursed with these sort of weird car issues. I hate electrical automotive issues since they're such a pain to diagnose and fix. Thanks in advance.