IAS = Integrated Active Steering
Meaning the rear wheels turn up to 3deg to make the turning circle smaller. Works incredibly well and makes the car turn a good 2 feet less than without it!
It's only available on non x-drive models though. I don't think you have it since you are running 315 in the back and I'm sure the tires would start to rub against the wheel wells at that point!?!
2009 750i individual | Citrin Black Metallic | Platinum Merino Extended Leather | BMW Individual Composition Package (includes Sport Package) | Dynamic Handling Package | Multimedia Package | Technology Package | Executive Package