Okay, I've given your game a little bit of a shot, and I think I have a few things to say.
I think the idea of letting go of the accelerator to help steer is a little bit flawed. Maybe you could implement an air brake system of sorts. As an Example, LT would help you steer left and RT would help you steer right while pressing both will slow you down for the more delicate steering areas.
There's also a long stretch of road that the finish line is on. It allows the player to get to the max speed of around 235MPH, and if I crash at this speed, I kinda just bounce off the wall like a rubber ball. Not sure how hard this'll be to fix, but eh. Now you know.