There's that old addage
If it's too good to be true it probably isn't...........
Just do a little research before buying. Don't believe what the seller is saying find out through other sources. Here are a few to consider.
Amazon.com: Supercharged! Design, Testing and Installation of Supercharger Systems: Corky Bell: Books
Amazon.com: Supercharging, Turbocharging and Nitrous Oxide Performance (Motorbooks Workshop): Earl Davis,Diane Davis: Books
courtisey of IMADreamer