Modding Spectre x360 BIOS (Tiger Lake)

I’m new to BIOS modding and the information is rather overwhelming so I thought I’d ask for some help. I’m trying to mod my HP Spectre x360 (i7-1165G7 with Iris Xe) in order to improve performance over its current locked state. In particular, I’m looking at accessing:

1) CPU and GPU voltage offsets
2) TDP limits

I’m currently on BIOS version F.10 (I can’t seem to post URLs yet but it’s sp111799). Instead of modding the BIOS image itself, I’ve been trying to directly alter the configuration bits using RU EFI (CpuSetup). So far I’ve tried changing:

1) Overclocking lock
2) CFG lock
3) Core/Uncore/GT/GTU voltage offset
4) Power Limit 1 (override settings)
5) Power Limit 1 (configurable TDP settings)
6) Platform PL1 settings

There are possibly a few other bytes I’ve tried altering but none of them are changing anything. For voltage offsets, I’ve tried a modest 32mv undervolt (0x20 with negative offset bit). For power limits, I’ve tried setting PL1 to 22.5W (0x000057E4) over my stock PL1 of 13W. I know that the chip itself can reach 28W by design though the current thermal solution appears to be viable for less (at least until power throttling begins). Checking with HWiNFO shows that while I can choose cTDP modes (Nominal/Down/Up), none of the power limits I’ve set are being enforced. For setting values I’m assuming that the data is in little endian format so I’m using “E4 57 00 00” to encode the 22500 mW power limit, for example.

Is there anything I’m missing here? Also, I can only find BIOS entries for the CPU power limits. Does anyone know if it’s possible to adjust the GPU?

Does BIOS Guard have anything to do with why none of my changes appear to take effect? I tried to dump my BIOS in FPT (running on an EFI shell) using "fpt -d aw200.bin -bios" and then flashing it back using "fpt -f aw200.bin -bios" but I end up getting an error about Protection Range Registers (error 167 I think).

I tried looking at the BIOS flags and it looks like the FPRR flag is already disabled. An MEInfo scan gives me this:

Protect BIOS Environment                         Enabled     Enabled           # Disabled=0, Enabled=1
Measured Boot Enabled Enabled # Disabled=0, Enabled=1
Verified Boot Enabled Enabled # Disabled=0, Enabled=1

I'm guessing BIOS Guard is on but I can't find any specific flags to disable it. I was hoping I could just use AMIBCP to unlock the power and voltage controls but even that route seems difficult.

I’m trying to do something similar for my wife’s XPS 13 2-in-1 9310 but I am still unable to undervolt. Did you ever make any headway?