[nextw33k]

As with current insurance, if you mod your car without telling them they will invalidate your insurance.

Once you do tell them you've altered the programming on the cars computer they are more than likely to tell you to find someone else crazy enough to insure you.

The self drive feature of a car is about to get very proprietary, like a flight system there is going to be assurances that the software the manufacturer installed is the same one that's running. Crash investigators are going to have a tonne of information from these cars (Assuming they don't blow up in a Michael Bay style crash).