Solved

Design points use

When choosing an engine, fuel or tire supplier, a certain number of points are attributed to our advantage or our disadvantage. For example, Murk offers 10 additional points in acceleration and 5 points less in fuel economy.
Then, when we receive design points after each race, we upgrade the cars. In the case of acceleration, when we get to 90 points, the overview of our car will show 100 since Murk offers 10 extra points. But, there is still the possibility of adding design points.
Should we continue to allocate points to go up to 110? Are these extra points taken into account in the performance of the car? Or should we stop at 90 because any additional point will be useless?

When supplier positives and negatives were first introduced the devs informed us that design points above 100 are ignored by the game. In your example above you should stop at 90.

max stat is 100 on each bro.
i would say before the season ends make sure you change Murk and have some design points to get your big4 stats on proper 100 without the + or - sponsor bonuses