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To my knowledge, if the flame front speed changes, ignition timing needs to change or it will, in theory, have a negative result. No ECU I know of does this automatically. If ignition timing is set to optimal for gasoline's flame speed, a faster flame speed will result in peak pressure too early and you'll have more negative work pushing against the piston on the end of the compression stroke, so ignition needs to be retarded. If this is done and the flame speed is really affected in a measurable way, it could help as much as 1-2%.
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The ECU in my Honda has a compensation table for air, fuel and water temperatures. Fuel temperature has virtually no effect on AFR - it's actually far less than the effect of humidity. I believe this is because the mass of the fuel is so small, the intake manifold is heated, and fuel gets up to air temperature within milliseconds.
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