iMac 2015 Firmware Pasword. Feel Like I'm S.O.L on this one ... help?

Now if this was my device i would probably remember the FW PW but i bought it as a spare or repair project, screen not working no external display output hocked it up in thunderbolt mode blindly as on power on i could hear the chime and was immediately asked for hdd password ... ok fine .... try to delete hdd ... obviously i can delete the hdd if i can't access it ... , pristine condition on the outside big shame for it to stand there ... idle ..." Furniture " no need to save data "Nuke and Pave" it is .... so i cracked it open and wiped the drives ... 1TB seagate and 1 32GB SSD figuring that the drives are formatted as fusion drives

( although Fusion is convenient for speed, all it is is a fancy name for JBOD "just a bunch of drives". With fusion apparently the OS / Boot Drive and a "smart cache" lives on the SSD while the Data lives on the HDD )

Now although i wiped the drives, still don't have display so i figured i would let this project sit for a bit more so i formatted both drives as Disk1 and Disk 2, put the machine back together, powered on, it chimed and the display turned on !!!

( well i could see the backlit has come on, but that's then my real problem materialised)

FW PW is persistent ... obviously out of warranty ... its about 3 years old now,

( i miss the old magnet assembly for the front glass Better Build and still quite feasible on this model ).

Apple want to change the Mobo and to do that would be paying double what i paid for this :( i can't get past the %#*@ firmware password....