Well, you’d need to empty the NVRAM where these settings are stored.
Unfortunately
- your NVRAM (actually both of them) is no longer in an ordered state (both NVRAMs have a full guid store, actually padding between entries and guid store is no longer an ‘empty’ padding but has an additional GUID as last line.
- you don’t have a complete firmware image, but just the bios region.
Dump the complete firmware either with fpt from C2. (CS)ME System Tools for the corresponding ME version or a hardware programmer.
If you open your complete firmware with UEFIToolNE it should at least look like this
Then download latest stock bios update from Lenovo, unpack it with innoextract, and extract the bios region with AMI_PFAT_Extract.
Left side stock bios update, right side your dump of the bios region, you see they’re a little different
Copy the marked AmiNvramMainRomAreaGuid and the following padding (0x30000 each) and replace both the AmiNvramMainRomAreaGuids in your bios region (0x30000 each) with the stock AmiNvramMainRomAreaGuid and padding.
Flash the complete firmware back with a programmer.
Be careful! You might brick your machine with a) messing with Lenovos anti- tampering measures or b) by damaging hardware when programming.