When the engine overheated, it set off some sensors that triggered your electronic control to adjust things. The first thing I would do is have someone take an OBDII gauge, read the codes and clear all codes and then see how the engine runs.
As mentioned, you could have a bad sensor but an OBDII gauge should be able to tell you that so that the sensor could be replaced.
The 8.1L engine has several internal safeguards and I am surprised that the engine did not shut down, or at least throttle down, when it overheated to protect itself.
You really need to find a GOOD mechanic that knows how to troubleshoot exactly what you have.