I see that they are selling performance chips for our cars on ebay. I was wondering what this does and does it actually work?

not too sure on what he is selling exactly. Description is vague. But my guess is just a fancy way of labeling an advance timing mod. All advance timing does it trick the ECU to think that colder air is entering the engine. Supposedly it is only temporary since your ECU will learn it. And if you want to do it all it is is a resistor you can get for like 30 cents or something. This is what i have picked up i am not speaking from experience. Since he says its custom made(another way of saying he made it). I recommened STAYING AWAY, same with every other "GO FAST' gimic that is sold on e-bay. I am sure someone might elaborate on what I said.

EDIT: I confirmned my suspicion. Check out the guys feedback(importmodifications) that should be enough to let you know to STAY AWAY.

The resistor taps into the air flow sensor, and fools the ECU.

we dun have an air flow sensor, we have an MAP, manifold absolute pressure sensor....

it messese w/the intake temp sensor to advance timing

I stand corrected...:)

So, advancing the timing....isn't that kind of what cam gears do? What would be the harm in fooling the ECU for this? Could you do both this and have cam gears?

You could do both. there is no harm in it(none that i ever heard of). But the timing advance is just temporary because your engine will "figure out" what is going on and it won't be effective anymore.