Lenovo Z50 70 black screen after changing settings in advanced menu

I flashed a modded bios which removed wifi whitelist and unlocked advanced menus, all was working perfect

Unfortunately I tried to permanently disable the discreet intel GPU by setting primary display to PEG (pci express graphics) but now the laptop won't boot and all I get is a black screen.

Things I have tried:

Booting with the novo button
Removing battery for 60 seconds and pressing power button for 30 seconds

Is there any easy method of resetting bios to defaults?

Thanks in advance