Intake plenum upgrade? Are they just larger, and how are they beneficial?

 

Coolingmist will knock off 200* with just water. To prove it to my self when I was pulling my 15K 5er, I put it on cruise at 70mph. I made the run at a hill two times withing ten minutes of each other. 1,200 with the coolingmist on and 1,400 with it off. In case your wondering, I turned around so I could go up the hill in the same direction. Same day, same temp, same wind, same, same, opps, the fuel gauge was a little lower. Does that matter that much?? LOL