Not always Bob, the stock air intake snorkle on the older mustangs(79-93) was VERY restrictive and therefore was subsequently removed by many racers. This little mod along with a free flowing filter usually netted around 15 hp. Not much in the grand scheme of things, but it was an increase none-the-less. The air passing through the intake snorkles becomes turbulant which actually cuts DOWN on the amount of flow possible. That is why mandrel bent exhaust is so popular. The noise is made, but the snorkle masks the sound by encasing it. So the noise is still there, but it is inside of the snorkle. Just like when you have your stereo on in the car with the doors shut. You can hear it inside the car, but (if it isnt turned up too loud) I cant hear it outside the car. Now, open the windows up and you have a free flowing car, with the noise escaping.