Is it fine to do something like this this video shows? He add a nut to the exhuast, so the stock exhaust will be louder. Some people said it will ruin the engine and cat, but some other said it won't do any damage because the spacer is behind cat. I know I should buy a aftermarket exhaust if I really want louder exhaust but I think this might be suitable for me. https://www.youtube.com/watch?v=0sq1vQrMHXo