Lead kills converters and O'2 sensors
The lead in the racing fuel WILL kill your O'2 sensor real fast, and your catalytic converter as well. Five gallons, if it were not diluted would be enough to do it. This will not set off a check engine light instantly, but will make it run too rich from that day on.......
The piston burned that was mentioned would have to have been on an engine that could not compensate fuel mixture for a very low specific gravity fuel that ran too lean compared to the heavy SG pump gas that has near .745 on no lead and .699 SG on C 14 racing fuel, big difference on jetting requirements, not the octane. I hope this answers your curiosity about leaded fuel in your emission engine.
Bruce