I think they put that rule in a lot of heads up classes to keep the cars looking more stock appearing. They are afraid people will show up with a pro stock type scoop or something like that and the car will look like a race car instead of a street car. The scoop I had on my car was just a standard super stock hemi scoop like what came out on the factory race hemi baracudas. I wouldn't have changed it if a nitrous backfire didn't blow it off my hood! I went with a cowl because I wanted to be able to run an air cleaner where I couldn't with the clearance of the other scoop. Also because I know that when I start winning some races they will whine about my scoop and make me change it cause its forward facing.