There is an active effort right now to reflash GM’s 12200411 PCM via open-source software - this should work for a lot of GM V8 vehicles in the late 1900s and early 2000s. Most of the excitement is toward the end of this thread:
The short version is that the kernel development and proof-of-concept app were done some time ago, but the app had some reliability and maintainability issues, and we’re now rewriting the app to address those problems.
I would love to get the Macchina M2 working with this project, but it’s not going to be a good option without support for high speed / 4x VPW communications. I don’t have the Arduino skills to make that happen, but I really hope someone else does… I’ll be very happy to add whatever is needed in the Windows app to support the M2.