Has anyone had any experience with these types of products? If you don't know what I mean it basically looks like a pop can with the ends cut off and some slotted fins inserted inside of it. The idea is that it changes the airflow into the carb and thereby increases fuel mileage and horsepower. It all sounds to good to be true and for the price they're asking ($60) I'm not willing to take a chance on it. Thanx for any info.