1. Hello, welcome to the forums.
2. Sorry to hear of your troubles
3. Here are 2 threads that may help. The symptoms sound different than what you are getting but at least a possible starting point:
P0300, high idle,
Limp Mode w/ codes - Tried multiple fixes / Searched
This last one may be able to lead you in a direction better than those 2 as it seems like it points out a few other threads:
Help me diagnose this problem: I can't rev past 3500 RPM intermittently (AK370Z)
Hopefully something there helps