I like my chip, and mine is a stick... Supposedly the automatics gain more from it, because it stiffens up the gear shifts. I haven't had my chip long enough to notice gas milage differences, but I do know you need a minimum of 91 octane fuel.
I'm assuming it will run like crap, but I don't know... I was told it requires 91 to 93. I know my 91 300zx runs terribly if you put the cheap gas in. I would assume it couldn't physically hurt anything considering the engine was made for cheap gas and only the chip has changed.
Be careful running low rated gas because you can risk the chance of spark knocking, which is not bad for small amounts of time but serious in the long run