How do I change car's hp?

There are many ways to change the engine power, such as increasing the RPM or the torque, adding a turbo or a supercharger (if it already has one then swapping for a better one), adding nitrous, etc. It's not like a number in settings you can change, it depends on many factors.

 

I just literally said you DON'T change it in files because that's not how it works, but if you want to risk your files getting corrupted then you can search for a tutorial on YouTube. I don't get why you would do this instead of like installing a mod for a better turbo or something.