SCT and the other tuner manufacturers charge big money for the software that allows you to control all aspects of the tune, so that's your first problem. And you have to have other hardware in addition to the tuner. And, as has been stated by others, you had better really know what you're doing to keep from damaging your engine.

Here's SCT's page describing what you need: http://sctflash.com/product_adv.php