At what boost level do you need to think about going to a higher octane?

 

^?

 

If you plan on pushing 13psi or higher you have to upgrade your fuel system. For example, injectors, and fuel pump. Also, you will need to upgrade your ECU. You will be fine with 15psi with 93 octane any thing higher you should use a much higher octane, to make sure you don't blow your engine.