Stuck on tier A...

I think I am stuck at tier A. I can’t beat the 6th race with Boss Shep. My car is at max stage, I can keep it perfectly on line, I can run a mistake free race, Shep never makes mistakes, but I can not come closer than finishing 1/4 second behind. I have made at least 2 levels to lvl 30 trying to beat him but gaining levels does not seem to make you faster. Is the game over for me?
Comments
1st race. Didnt finished. Just checked when he uses Nitro.
2nd race. Easy win.
Could be better if there was some info which another races has changed too
2- swing to outside of corners and cut toward center then don’t oversteer coming out of corner
3- save the nitro boost until you hit the sandy beach