Yes, the chip can be replaced, and the chips are programmable, but you can't flash the ECM like on new OBD-II cars. You have to remove the chip, stick it in a programmer, and then program it in the same classic manner of programming EEPROMS.
Though 99% of the aftermarket "performance" chips for the Fiero are a waste of money. If your car is stock, you don't need to change the chip from stock, unless the stock one is bad. Then you should replace it with a good stock chip/program.
So it wont make a difference if i put a programmed chip in it? I only have egr block off and performance exhaust with out cats. Little quicker than stock right now. Anyone have any ideas for little power gains? Thanks