I just started playing Live For Speed, that game is so addicting, even the multiplayer demo. The cars are made up, but you can tell what they're based on, kind of like the cars in Grand Theft Auto, but the physics are really great, and the drifting is really fun, and there are so many things you can adjust.
There are three cars in the demo you can play with online. There's a FWD compact, an NA version of an RWD car that's based on an FC and a Starion Conquest, and a turbo version of the same car, that's what I play with.
You can mix your own colors, tune the suspension, pick tires, adjust brakes, and all that fun stuff.
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http://www.lfs.net