Fixed the link for you as it was broken.
Ok, onto the actual "chip". That's not a chip first and foremost. It's a box of resistors with some wires you hook up to the output side of the air flow meter harness. What does it do? It tricks the car's computer into thinking the car is getting more/cooler air than it actually is therefore telling it to send more fuel, effectively making it run rich all the time.
Does it work? Sure, you might pick up a couple of horsepower, but honestly chances are a lot higher that you'll be picking up bits of engine off the street than horsepowers with this modification. Stay away from it.
You want a chip, buy a real eprom, yes, it's 10 times more expensive, but that's because someone didn't just slap two resistors and 4 wires together; someone put time into programming the fuel maps to gain performance. Dinan, BavAuto, Confronti/Turner, EAT ... all good brands/places to buy a chip from.
edit: You could buy the parts needed to make that thing from Radio Shack for 2.50.