[LM24] Difference in top speeds at Le Mans

[lemanfan]

Can anybody explain differnce in top speeds at Le Mans specially between years 1998-1999-2000. In 1999 closed GT1 cars run 350 kph and in 1998 and 2000 they did not do more then 330 kph. I know that in 2000 there was no closed prototype but when you look at the year 2001
when Bentley did 335 kph it is still much lower than in 1999.
In know that it could not be due to horsepower because all these cars produse around 600HP.To run 15-20 kph faster you need around 100 hp more or reduce drag coefficient for example from 0,5 to 0,42 which is a lot.