Asus Z790 Dark Hero PCIE Configuration question

[xaeret]

I want to know if there's a way i can disable PCIEX16(G5)_2 Slot so that my GPU can run at full x16 when i need it to (in very specific tasks, which is why im hoping its possible in bios)

Current Motherboard Layout:

M.2_1 = EMPTY
PCIEX16(G5)_1 = IN USE - ASUS RTX 4090
M.2_2 = IN USE
M.2_3 = IN USE
M.2_4 = IN USE
M.2_5 = IN USE
PCIEX16(G5)_2 = IN USE - 8 SLOT NVME PCIE CARD (stealing lanes from G5_1)
PCIEX4(G4) = EMPTY

Because G5_2 is in use, my 4090 is running at x8 instead of its capable x16.
i want to know how i can disable G5_2 so that G5_1 has access to all 16 lanes. how can i accomplish this WITHOUT removing the device?

[MrAgapiGC]

mmmm! is a odd inquire.  check : On bios  ADVANCE, ONBOARD DEVICES CONFIGURATION, there is something called CPU mode configuration Mode IF there is something Called PcieX16_1 ONLY. if not then no! 

[xaeret]

in that setting there are only 2 options: auto OR PCIEX16_1 + PCIEX16_2.
i attached a photo with the bios description of the settings, i've only tried auto as i imagine the other just does what auto is currently doing

[MrAgapiGC · Accepted solution]

then the answer is no. sorry user. most of that section is very automatic control mostly board cpu. also all this board we use are consumer.  There was a time long time ago this where possible when cpu support it like x99 x299 boards. for example that have more lanes with switches. and this is not something we can add a switch or on bios functions. On both amd and intel  consumer boards

If you need to have the 16x on the gpu you need to remove and use other nvmes on external solution.