http://www.whipplesuperchargers.com/faq.asp?faqID=3
"Supercharging increases air density and significantly increases power on an otherwise stock engine. In short, supercharging makes a V-6 perform like a V-8 and makes a small block V-8 perform like a big block V-8. OEM manufacturers like Ford, GM, Mazda, Mercedes, and Jaguar offer factory installed superchargers on several models due to the tremendous benefits. Our supercharger systems offer more torque and horsepower per dollar than any other single engine modification. Most other modifications available require specific matched parts, in-depth tuning, are not smog legal, and won't produce the performance gains you'll receive from just the simple addition of a supercharger system"