I'm not surprised that latency hiding is causing weird things to happen, I'm not sure if there's anything I can really do about it from my end.
I'm teleporting the car every tick, and the game doesn't know to predict that.
If you hold spacebar while driving, does it help? You would lose latency hiding, but it should still make the physics manageable, like in 1.1.
Worst case scenario you might have to stop using the mod for now, which I'm sorry to say.