Can't get past the system lock PIN code
There are multiple options available.  


You can purchase a EFI Rom chip for your particular model computer, attach it to the logic board and it will bypass the system EFI.  http://www.cmizapper.com/components/chips.html
You can attempt to rewrite the existing EFI chip  https://ghostlyhaks.com/blog/blog/hacking/18-apple-efi-bypass
You can attempt to brute force the password with an Arduino Teensy https://github.com/orvtech/efi-bruteforce or similar. http://www.cmizapper.com/products/brutus.html