If you want to:
While the mod offered chaotic fun, recent game updates have officially patched this extreme exploit. Here is a look at how the 400 km/H mod worked, why developers patched it, and how you can still safely push your truck to its limits today. How the 400 KM/H Speed Mod Changed the Game euro truck simulator 2 speed mod 400 km h patched
Modders edited the .sii data files to give truck engines an impossible 10,000+ horsepower. If you want to: While the mod offered
Change thrust_characteristic_curve values to allow maximum power. However, a word of caution: Using extreme speed
If you have a legendary 400 km/h speed mod that you absolutely refuse to give up, you can freeze your game in time to match the mod.
To get it running, you typically drop the .scs file into your mod folder and prioritize it in the Mod Manager. However, a word of caution: Using extreme speed mods can sometimes glitch your "total distance" stats or cause issues with economy plugins.