[REQUEST:] Modded BIOS for Toshiba Satellite Dynabook B552/F (Pro S850)

[hiriotapa]

    Me and my son are living in Thailand and we've bought an second hand office laptop for him, imported from Japan. It's a Toshiba Satellite Dynabook B552/F, also labelled Pro S850, from 2012. It has an Intel HM76 chipset, i5-3320M CPU, Intel integrated HD4000 graphics, Mini-PCIE 2.0. Now we're trying to install a desktop GTX970 as EGPU through a Mini-PCIE to PCIE x16 riser card, which does seem to work with a lot of laptops. The problem is that it doesn't recognize the GPU as Basic Display Adaptor, as it should, but as an Unknown Device.
I suppose this Toshiba laptop whitelisted the Wifi-card that came with it and blocks other M-PCIE cards. Am I right?
So now we need an unlocked BIOS, with more settings, so that we can make it recognize the EGPU on the Mini-PCIE port.

However, I can't find any modded BIOSes at all, only the original for A5A003305 FHFLSY1 mainboard at:
https://drive.google.com/file/d/115vzCHs...sp=sharing

The current BIOS is version 6.10, EC Version 1.00. In System Info it says that Toshiba is the manufacturer of the BIOS. Date of the BIOS is 26/09/2012. The BIOS screens do, however, look very similar to those of L850 and C850 Insyde BIOS.

I did find a version 6.60 BIOS update for the B452, B552 and B652 models on the Japanese Toshiba support website at:
https://dynabook.com/assistpc/download/m...ndex_j.htm
but unfortunately it doesn't work and gives an error: This computer is not supported. I did, however, manage to extract the Toshiba .COM BIOS-file, by opening the .exe file with BIOS_V660.exe /extract. Converting the BIOS to .BIN by using ToshibaComExtractor doesn't work. I only get a blank screen.
https://www.mediafire.com/file/kiw5uqch6...T.COM/file

Can someone help me and my son unlock the advanced menu so we can install the EGPU properly and he can use his GTX970? My son is saving for a desktop, but it will probably be only next year that we're going to buy one for him.