About the problem with the FNDR objects used for the brakes calipers, have you made the _M copies of those objects? They're always required to don't make the car crash in-game. The .dgbangerdata files for them are obviously required, you can take them from many add-on cars.
And how are the traffic and pedestrians densities? If they're the default ones or the traffic one is set higher the game crash is given because of the much more polygons of traffic and city cops. To don't get it is required low the amounth of traffic, pedestrians and maybe also of the same cop cars. Is already known how the game has limits in manage polygons while loading the city and all the stuff in it.When I try to cruise with the max level of cops, the game crashes. But when I cruise with the lowest level and without them, it doesn't.