then just the whole game probably isn't something for you, becouse single player allso runs 25 fps max, and yes you can ofcourse switch off the framelimiter, but the game doesn't refresh with this limit, but it builds on this limit, the game doesn't get shocky animations etc becouse, the whole game runs slower, so you can play single player good on a bad pc becouse everything justs gets some slower, and not unplayable by the messed up animations and enviroments.
you get the same with a higher framelimit, then the game will run unnaturally fast, and so will the npc's react and you drive and shoot etc, so it will only get harder to make good stunts then.