I also think it would be a good idea to consider having a Visibility stat for each vehicle, that determines the result of a random "Get pulled over roll." done each time you travel.
Somthing like:
Vehicle stolen: +3 Visibility
Bad driver: + (Somthing relating to the driver's skill) Visibility
Vehicle carries heat: +(Some math related to the amount of heat) Visibility
Good driver: -(Somthing relating to the driver's skill) Visibility
Obvious upgrade (exterior armor plating or such): +5 Visibility
Suspicion of vehicle (As a liberal wearing an elephant suit in the Intelligance HQ is going to be looked upon with suspicion, a HMMWV being driven to the Genetics Lab is going to look really strange): +/- (Value would vary) Visibility
Should you fail this check, the liberals will get flagged down by a cop. You could either try to outrun the cop or pull over. If you pull over, you get a chance to:
A. Surrender
B. Bluff the cop (Depends upon persuasion of driver.)
C. Bribe the cop (You lose some amount of money that can be reduced by Street Skills, with the chance of the bribe being accepted lowering as Police Regulation gets closer to L+.)
D. Attack and drive off. (The driver makes a single attack against the cop. If the cop is incapacitated or killed by this attack, the liberals get away. If the attack misses, the cop gets a single attack against the liberals and begins chasing them immediately. If the attack hits but does not incapacitate or kill the cop, the liberals get a single "free" driving turn.)
I would also suggest the addition of a Chop Shop to the shop areas, where you can sell/upgrade cars. Upgrades would be things like:
Passive armor plating: Minor boost to protection, is not apparent from the outside.
Active armor plating: Major boost to protaction, is apparent from the outside.
Snow plow: Assists in ramming checks, looks a little strange.
Car battering ram: Greatly assists in ramming checks, looks very strange.
Sidecar (Motorcycle Only): Allows up to three (as a second liberal could hold onto the first normally) Liberals on a single motorcycle, reducing speed.
Nitrous Oxide Tank: Boosts speed in car chases. Comes in Inconspicuous Small (1 Turn of boost) and Suspicion-Arousing Large (3 Turns of boost).
High-Horsepower Engine: Permanantly increases speed.
Armored Tires: Permanantly increases duribility.
Bulletproof glass: Permanantly increases protection.
Tinted glass: Permanantly decreases visibility.
Rocket Propelled Grenade: A very expensive, very illegal (Except at C+ Gun Law, of course.) weapon that can only be equiped to your car. Spare rockets can be bought, but only one can be in a car at a time. If activated, all liberals but the second attack normally. The second fires the RPG into your chasers. Mob conservatives (Hicks, Rednecks) are likely to back off even if they don't get hit. Some things just aren't worth it. Police have a lesser chance of doing the same. Mercanaries have a low chance of it, while the Death Squad and CIA do not. And, of course, it wouldn't be very FUN if there wasn't a chance of Conservative Critical Failure in using the RPG, crashing your car instantly.
I also suggest, because it would be awesome, that a Professional Racetrack where high-quality cars can be stolen be added to the city outskirts.