Thank you.
The overall performance of the GTE is now on par with my URD GTE but I find the top speed a bit low at 275km/h.
So I added a 7th gear in drivetrain.ini in the [GEARS] section:
- change COUNT=6 to COUNT=7
- after GEAR_6=... add the line:
GEAR_7=0.8000
Now I can reach 303km/h on the Mulsanne straight (no chicane).
(don't ask me how it works, I'm just a noob playing with a text editor :-)