I run Sunoco 100 race gas in the car... Not sure it gains me anything, but it doesn't hurt the engine. All the plug tips are still showing signs of a very lean condition (white deposits).

When we were kids we filled an old rotary Mazda with diesel accidentally and trashed the engine within 5 miles... So I can safely say, don't drive the car at all, drain the tank and purge the fuel system. Otherwise you'll be looking at buying a new engine...