I usually just raced the computer in a quick race (not in the career) to see what my car actually would run if it had been staged properly.
As far as the traction issues, I do agree. It became quite annoying trying to get a 700-800whp RWD car to go in a damn straight line. I'd play with the gearing, but then the car would just bog. It's like there's a switch, bog the tires, or spin like a sonofabitch.