Thats a lot but yes, I'd bet its the cold fuel. Engine masters did an episode trying to see if icing the intake helped, I forget all of the details but what they found was that it helped but it was because it made the carb bowls cold and the fuel was actually cooling the air charge alot, not that the cold manifold was lowering the IAT. The actual temp of the manifold was almost completely insignificant, but the fuel temp was important.

Remember everyone used to run those moroso cool cans?