I would be up for that to see if it is my driving style or I am not getting the best from my tuning
I also recommend time trials. Go to the Arcade mode, pick a stock car, adjust the driver aids for your style, and run 10 laps on an unfamiliar circuit. Within 5 laps, you should've discovered something (a driving line, braking point, rhythm) that you didn't notice before, and within 10 laps you should have a basic understanding of the track. Occasionally take a mental note of your sector times.
When you're done, watch your replay, and take some notes. Record each of your lap times to get an accurate measurement of your consistency. Do your times vary by seconds, or by tenths? Watch your sector times to see where and how you left time and speed on the track, and try to gauge what a perfect lap time would be and what it should feel like.
Then, when your done with that, smoke a cigarette and relax. If you don't smoke, or whatever, do something different for about 5-10 minutes, and reflect on what you've learned. This will help recalibrate you from
velocitation.
After all that, try 10 more laps on the same track with the same car. Compare your results, and you should get a pretty accurate idea whether it's the car, or it's you.
...at least, that's how I did it. I'm not the fastest, but for using a DS3, I'm not bad either.