Why? get better gas mileage.
How will it get better gas mileage? It will use more EGR when lifting (partly) the throttle (I.E.: on a decline when the throttle is partly lifted) so that engine braking is reduced (manifold pressure increased*). If manifold pressure is increased*, the engine is performing less braking, less braking equals better mileage caused by having no oxygen in the combustion chamber. No with no oxygen, there is no fuel needed to be burnt. Therefore you get better gas mileage.
*Increased manifold pressure is used in the correct way, meaning pressure is closer to atmospheric levels. When the engines idles, when vacuum is at near maximum, at around 5psi. If one atmosphere is 14.7 psi, then there is a vacuum, or less pressure in the manifold. If you increase pressure in the manifold, you get closer to atmospheric pressure of 14.7 psi, where manifold vacuum is nearly non-existent. Enough with the science, if you don't get this, it doesn't matter for the installation and tuning part.
Here is where I got the idea: http://www.autospeed.com/A_110555/hD...s/article.html
The guy got 3 percent better mileage with his Honda Insight, I bet we get better results with the Aveo. The Aveo, believe it or not, uses the same EGR system as the Insight. The system uses a sensor and lift valve.
How it works: If you alter the sensors output to make believe to the ECU that the valve is less open, the ecu will open the valve more, letting more EGR flow.