well its good to know how to do this. i was not familiar with either of these i did some reading. looks like clover supposedly does this for us by reading the SMBIOS now. i don't have either of these vars in my nvram. and perhaps yours were out of date and overiding the SBMIOS values? one may need to remove them from nvram.plist and let clover generate the stuff by populating/reading SMBIOS.
from the wiki - says that these 2 vars (MLB and ROM) are now deprecated and clover generates a SMBIOS string with these. clover-genconfig will spit out the MLB value for you.
ioreg -l |grep SMBIOS
cut and paste the stuff between <> and run through xxd -p -r and you see what this byte string has in it.
well yes. many of us have done this without issue.
flash to real bios v1.46 and then flash with modded bios v1.46. (i did on my 2 boxes) see post #2036738 on this.