The COLD Hyundais are not your best work, namely the 2nd, you really went overboard with the hue.

1st is a pretty decent shot, but for an action shot there's not much action going on. Remember to work with the tools GT4 has in photomode.
In this case, a speed of 1/125 (the default) could work well, making the wheels appear spinning fast and motion-blurring the scenery, to get the idea of movement. also a smaller focal distance (it appears you used the 22 - max, maybe with 8 you'd still focus the entire car while already achieving a good road-blur) would focal-blur the road ahead, giving it more depth and making the shot more 3D-like. 👍
The HOT shots are way cooler, namely the 1st one. Good tones and the rims actually look good, even on photomode.
2nd shot would definitely look better without the stage spotlights coming from the rear lights.
I really like the contrast levels on your 300SL entry shot, also cool angle. 👍