I did it because 1, I figured it was bolted to the body originally and I had my just laying there, and 2, I noticed it ran different when I set it on the trans while running on the run stand. The ecu supplies ground for many different sensors. It made sense in my head that it needed the case grounded.
Hey, that's awesome input. I will ground the case. My buddy said that my engine bay "looked like Bill Gates threw up in it!" so I'm gun shy of adding more wires, but of course I will :)