That peak at 500 iterations is where the numerical schemes change from first to second order.
The car with the good stls you submitted worked for me. I think you have issues because of, as you say, your massive RAM. You will need more.
But you were able to use CFD so well now, that you can now learn that creating the front downforce is one of two big challenges here. Your CoP is indeed pretty far behind. However you have the same issue everyone had with cooling. Getting the air through the radiators is challenge number 2.