reverse brake speed is only activated when positive so give it a zero, you said it still does that but it’s not true, the code is quite simple, you can check it in AFGearVehicle::substepTick.
I believe you have your own changes, if you can recreate the problem in the example project, let us know.
we have removed engine friction from the engine power calculation so the input curve directly defines the power output now.
ABS is a bit different now, you mean with full ABS does the vehicle understeer and without ABS you get oversteer?