Hi there from NYC, NY
When you operate your vehicle, it is controlled by several computer systems. Your ignition system runs with one (it is called your ECU). The rechipping basically changes internal mapping structures for the performance of your engine. What does that means? Most new chips offer increased performance and power mainly in the mid rpm ranges. One offers better gas mileage. Shop around and keep your BS meter on. Your actual mileage will also vary based on your driving style.
Rechipping will give more recent updated information based on hit-and-missed data from the chip manufacturer vs original factory (more anicient and more conservative )settings.
Shopping around will help. One thing, LandRover rechipping is expensive, try to have one that will default back to conservative factory settings.
By the way, check out my thread about OBD II readers. I have some links there.
Adam
