Even if you manage to get a maximum heat exchange of ten degrees, the rate of heat exchange of sprayed fuel inside the port to the combustion changer would be negated. Remember, even with a fresh charge of cold air, the fuel mist is so fine that the heat would travel through ti quickly, regardless of a 10 degree temperature change. Also the distance from the port to the chamber, the immense heat remaining in the chamber from the last combustion also be contributing factors that would negate the heat exchanger. Save your money, even if there is enough temperature change to reduce the temperature of the fuel the change would be tiny as well as the performance gain.
