What's an immobilizer chip?

Looks like I've about decided on the V6!

Really like the way it drives, more like a Passat or BMW. While the 4 feels like a "cheap" Honda.

Other features that you get on the V6 that you can't get any other way:
- HomeLink (remote garage door opener built in)
- Steering wheel radio control
- Climate Control (mentioned earlier)

Have also settled on a 2000 model. It's the first year for side airbags (leather or V6 only) and for child-seat tether anchors.

Still a bit concerned about MPG. Anyone else care to post their MPG ratings?