I want to remove some mods after I played and build some mod's stuffs (like pipe in buildcraft). If I just delete mod, minecraft launcher will get error at start (It say something like missing block ids or can't map block ids or something like this.). Is there any way to just remove it or replace mod's stuffs with something like sand when remove mods.
edit: I forgot to mention that I want to fix it on my server not single player game.
ps: Sorry for my bad English.