I ran a Dizzy stage 2 and a Dizzy E30 for over a year and never did a single data log. These are "off the shelf tunes" just like the Cobb tunes that came on your accesport (only better in my opinion). No Datalogs are needed but Dizzy will give you one free just to see how it's running on your car. If you are purchasing a custom tune, then the datalogs are not an option....they MUST be done.