Hey, I want introduce corruption in the game and change penalties that are imposed on the empire, when the city cap is exceeded.

I wanted to decreese ammount of FIMS that produce all cities empire.

Something like:  production := -(CityCount+1 - CityCap)/CityCap *100%

However, I havn't found any related assets.

Hello! IIRC, City Cap Penalties are in the tag_empire_major descriptor inside the empire folder (Empire_bonuses IIRC). Search for that file in the overwrite menu.

Thanks