Misfire questions
 

How does an Ecotec know it has misfired? Does it manage to sense and/or record every instance? At what point does it set P0300 or P0301-4. At what point does it light up the CEL. Is it possible to sense a misfire that isn’t real?

AlGorerythms. Basically, it monitors the crankshaft looking for variances. A lot more complicated.
Misfires are not necessarily real misfires, one of the sensors involved is a microphone (knock sensor). P0300 does not mean "random" misfire, it means unidentified misfire. It usually takes 2 times before it identifies which cylinder.

Are you saying detonation or preignition might show up as “misfire”? That would be extremely useful to know. I had only considered no ignition.