hello Pawel, you must install the mod in this folder : ...\Documents\My Games\Sid Meier's Civilization 5\MODS what do you mean with custom map ? if it's a map made by you or another player perhaps it's the map that has a bug? If not, it is possible that the mod is not compatible with some maps. It is probably because of the new resources but I really don't see how to change this if it's the case! Did you try the mod with a normal map from the game ?