Too much timing?

Incomplete burns.
Part of the reason for left over HC is 'heavy' components of gasoline take more heat to vaporize.

For example, this 8% eth fuel began to vaporze just over 100 degrees F, same as the non-eth. But it required over 300 degrees to vaporize the last 20% of the fuel.
It needed over 400 degrees to completely vaporize all of the fuel.
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Race fuels are different. Most finish vaporizing at lower temperatures, even oxygenated ones.
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