Before I jump in, I'm not a professional tuner and I just love old gmt800's. I don't plan to tune for the public, don't wanna tune for the public and...
Water/Meth injection is an option for reducing intake and and charge temperatures. I haven't personally used W/M injection, but I know several people...
Doesn't sound like it's actually autostop mode in what I think of as autostop (shutting off at redlights). Maybe just something in a left over piece...