Did you tell the tech about the fuse incendent?
Did the tech tell you what did he check?
Is the idle ok now?
Check the idle speed solenoid when you are having the erractic idle, is the solenoid plunger moving in and out?
The tech should at less hook up a scanner and see what else is affecting the idle. The EGR (Exhaust Gas Recirculation) valve will affect the idle, but that will only happen over a long time and very rare, also it has nothing to do with what you have mention at the beginning of the thread.