The maximum Boosted CLAAS Lexion 8900 mod is "Realistic."
Changing the engine simply changes the engine and side stickers; the 8900S is the default engine configuration.
In my Lexion 8900S:
The vehicle's fill volume was increased to 34,000 with the actual redesigned look; the diesel volume was increased to 1,550; the maximum engine power was increased to 990 HP; the driving speed was increased to 50 km/h, only with the top engine (working speed is standard and depends only on equipped tools); the discharging and unloading speed was increased three times; the thick pipe effect was redesigned; one more crawler was added (for a total of two options); and the option to choose the hull and wheels was added.

Thanks to Kot77