for t5 suite? It's pretty stable. Not sure what repo you're talking about but essentially they have backwards engineered the ROM on the ECU's to make tweaks and adjustments. It's a very flexible system from what I understand (though I haven't tuned with it at all, I do have one car where the computer is from a 2001 and it's backported into an 80's saab)

Oh I see. I misunderstood and thought you were saying you were going to control it with a Pi Pico. Read too fast.

No, for the cruise control chip? I am thinking a ATtiny85 or similar. It'll need some breadboarding since the inputs and outputs run at 12V, so some voltage stepping is required