He's what happened.

Cold weather...

More knock...

You went WOT...

Your CEL started flashing...which led too...

Piston or Pistons chipped...

You got lucky the chip or chips basically disintegrated and went into the oil pan...

Now you just have a P0300 random misfire code from the pieces of piston or pistons missing but your motor still runs and you're revving the crap out of it...for now...

Go yank the plugs...as we are still waiting for those pictures.