@Stan Galat, @DannyP mentioned above that you might be using a Megasquirt ECU. Just curious if you're heading in that direction. I ran the MS II in the old turbo for years. As I'm sure you know, it has a few more features enabled than the Speeduino and is an excellent, reliable box (I bought a spare and never used it in 10 years of driving).
Tunerstudio and Megalogviewer are the same software interfaces for both. The firmware loaded into the ECU determines the menus and features enabled in Tunerstudio. The forum support for Megasquirt is massive while Speeduino is catching up. Many questions I had about setting up Speeduino were answered by searching the Megasquirt forums. Firmware updates on Megasquirt II are less frequent than updates on Speeduino. Speedy is VERY open source and the main developer of the hardware and software has been holding online classes on how everything works and how you can change it if you want to (preserved on Youtube). Those are the main differences. I'm comfy with Speeduino as a lower cost solution, but the Megasquirt boards are extremely capable and mature.