At the risk of getting tree'd, these hacked cars are basically cars with insane amounts of power and speed. They can be useful in that the fastest cars have negative PP and so can bring in big rewards in seasonals with PP bonuses, and also in that they are among the only ways you can beat another hacked car. They can be used offline. Hell yeah, they're faster, some of them get up to 1,000mph! And finally, the community is a bit angry with these sorts of hacks because it was due to these that many other types of hacking was patched,