318 MAX fuel economy builds?

Higher temperatures vaporize more fuel -- good for fuel economy.
Lower temperatures facilitate slightly higher VE at WOT -- good for WOT.

I tried heating the intake air on carb and PFI engines. I found warmer air helped MPG in wet flow (carb/TBI), but cold air and heated fuel actually worked better on PFI. PFI usually doesn't suffer from vapor lock, so up to engine temps work well and don't kill parts. If you have a return line, you should run a fuel cooler to keep vapors down, and prevent softening a plastic fuel tank. The longer version:

Combustible Caliente (Heating the Fuel) | Ecoceptor