Can I get away without Toyota parts for plugs, injectors, or coils?

Throttle body replacement is the only known repair method for Throttle body position sensor, because there's no way outside of the factory to calibrate if you just swapped the sensor.

Sounds to me like there's no new problems with your car, just same problem you had before with unstable idle and you'll likely find P1121 again. Just put in another used throttle body from the wrecker. It's just some plug, nuts, bolts, clips, very easy job....

 

... and of course, the correct cookie cutter text for a P1121 is Coolant Flow Control Valve Position Sensor Circuit Stuck.

There are plenty of posts in the Gen 2 forum about that, some of which will have the repair manual except for how to troubleshoot and repair this problem.

This code will be set if any of the following conditions are detected:

• Water valve position sensor output voltage:
  • No change despite the ECM sending a valve control signal or slow response
• CHS tank outlet temperature sensor output:
  • 60°C (140°F) or more (when hot coolant recovery starts)
• CHS tank outlet temperature sensor output:
  • No change despite the hot coolant being recovered

 

Oh heck, was this another of the "somebody googled a P1 (manufacturer defined) code and got the meaning it has in some other model of car" stories?