To download the latest software: 1. Type in http://www.holley.com/TechService/Library.asp (or go to the top of this screen adn click "Technical", then "Resource Documents and Downloads") and scroll down to "Fuel Injection". Click on "Pro-Jection 4Di Tuning Software". It will ask you to "Open" or "Save". Click "Open" and you will see a folder named "4Di Software". Click on this and look for a pdf file named "Instructions to Download". (If you do not have Adobe Reader, you can download it free at www.adobe.com) Follow these instructions to complete the download. 2. The software is now installed.