What is happening is that the game’s assessment of your driving
can be improved by this particular part that it is now offering to
you. I do believe that this game bases a lot on real life so I
think what this part is supposed to do in real life will do so in
the game. For info, I’m not sure if there is a website that will
cover all the parts in the game. Try going to the individual
manufacturer’s website. The game assess you for every race. So if
you one day decide to play bumper cars with your friend, the game
is going to think your driving really lousy and offer you some part
which may not help at all, so be careful.