[flipper35]

There is a noticable difference, even at idle, since you aren't pulling in all that hot air from under the hood. I used to set the idle, close the hood and the idle would change so I know it was pulling in lots of hot air. Now it doesn't. I don't think there is much ram air effect, but it all helps.

There isn't any interference since the al plate is on the same plane as the bottom of a regular air cleaner plate. The foam the Moroso closed cell stuff for hood scoops available at your local speed shop or mail order company. It was $13 for the al sheet and the foam was pretty inexpensive too.