[t vago]

Your safest bet would probably to heat up the intake air.

Given that gasoline has a specific heat of about 2.22 kJ/kg*K, and air has a specific heat of about 1.01 kJ/kg*K. Gasoline takes more energy per unit mass to heat up, as compared to air, but your engine does ingest 14.7 grams of air for every gram of gasoline, so there is that.

Here's a quick thought experiment: Let's say that you have 14.7 grams of air in an easily manipulated can, and 1 gram of gasoline in a separate container. Both are at 0 C. Heat the air so it's now 40 C. The gasoline temperature can remain the same. Now, mix the two together so as to obtain a uniform mixture. You will find that the temperature of the mixture is now almost 35 C.