By default, RPG Maker imposes a limit of 120 FPS on the game. This means that if you tried to go beyond 120, it would simply round it down to 120.
This script removes this limitation and allows you to run your game at speeds that your machine can handle, enabling you to potentially test your games faster.
Script: download here
In the script editor, place this below Materials and above Main.
To change the frame rate, make the script call
Graphics.frame_rate = x
Where x is the frame rate that you would like to change to, such as 60, 120, 150, and so on.
60 is the default frame rate. You may notice some lag when you jump from a high FPS to a low FPS.