I would have thought the whole fuel system would be at risk, pump, rail, injectors.
I made a fatal error when I was in Germany a few years back during the World Cup. I filled up half the tank with the black nozzle - when some woman starts waving and shouting something in German, so I stop filling, thinking we had to pay first, my dad, in a rush, pushes me out the way and keeps filling to the top.
Granted, his car was a Diesel - but we filled it to the neck with 2 stroke mix!. This was at 10pm at night, so we couldn't drive the car anywhere. I had to sleep in it, then push it down to this car garage just down the road, they flushed the tank for 10 Euros!