Hot Air Intake (HAI): Keeps intake air temperature hot even when it's cold outside. I haven't fully figure this out yet, I know that it's a thermally controlled valve on my air cleaner housing.
This prevents carburetor icing and speeds cold weather warmup. I highly recommend keeping it. If it's plumbed correctly, the flapper opens when the engine is hot to let cool air get to the engine.
Colo Springs, CO