I sell and support the Holley EFI products and I'm Holley certified. I also teach classes and offer a fairly inexpensive ($75) online course that has been a lot of help for people starting out with Holley. I sell the HP as a kit with all the harnesses, etc. included. The Dominator is ala-cart. The HP is the same internal ECU as the Dominator with the same software. The Dominator adds: much more I/O, DBW, dual wideband support, and auto transmission control. If you're a racer get the Dominator because all the extra I/O means you don't have to buy a separate data logger. Call me with questions.