Windows version available from the resources section of this forum for free and android version is from google play store for approx $10. Also lots of info and download at tuneecu.net
Bear in mind that altering the speedo reading also messes with the ODO reading. If you've changed the DIFF - I'd try and use a different speedo all together (maybe GPS!)
Did you fit 2015 wiring or is it still a pre-2010 ECU?