You're not really going to find anything but raw hex and some disassembled stuff. None of it will be in a language, just instructions and neumonics native to whatever processor is used. So you aren't going to find something in C or whatever, all of this stuff is reverse engineered and the source isn't available because it belongs to the manufacturer.. If it was, you'd see some sick mods being done, not just tuning..
There is a reason it's sometimes easier to make your own standalone than try to hack something existing..

If you're looking for a good starting place, I can point you toward some 88-91 Civic stuff, the ECUs use 8051-family processors so they're a good thing to mess with.