I put in the complete kit as that is the only way Bob sells it and as I'm in the sunny part of oregon, haha, lots of snow I thought the pre filter was a good idea. Still too early to tell what happens to mpg or egt's but will keep you posted. Cost about 3 bills but I felt it was worth it as I didn't want to do one of the "home" mods. They probably work as well but I like the look. As someone said on this forum why be cheep on a $33k to $40k truck