I didn't think manifold heat was important until the weather got cold this year. After putting up with the truck spitting and sputtering and carrying on, I finally fixed up my heat riser, which had been stuck open. WOW!! What a difference. I thought about water heat, but you don't get the heat when you need it (when the engine is cold), and you get heat when you don't (when the engine is hot). I think the factory's thermostatically controlled heat riser is the way to go.
