Hello. I have a Lenovo l340-17irh with i7-9750hf that SHOULD support 2666mhz ram
but Lenovo locked it to 2400mhz for some reason (the ram stick itself is 2666)

so I decided to do IFR modding

i found the right FPTW version and did fptw64 -bios -d bios-region.bin
then I loaded it into UEFITool and searched for one of the bios options, then extracted body to body.efi
loaded it into ifrextractor and got the IFR

I indeed found that its set to 2400 in the bios vars

0xAD48A One Of: Maximum Memory Frequency, VarStoreInfo (VarOffset/VarName): 0x147, VarStore: 0x2, QuestionId: 0x221, Size: 2, Min: 0x0, Max 0x1838, Step: 0x0 {05 94 A1 11 A2 11 21 02 02 00 47 01 10 11 00 00 38 18 00 00}
0xAD49E One Of Option: Auto, Value (16 bit): 0x0 {09 08 E7 0F 01 01 00 00}
0xAD4A6 One Of Option: 1067, Value (16 bit): 0x42B {09 08 A3 11 01 01 2B 04}
0xAD4AE One Of Option: 1200, Value (16 bit): 0x4B0 {09 08 A4 11 01 01 B0 04}
0xAD4B6 One Of Option: 1333, Value (16 bit): 0x535 {09 08 A5 11 01 01 35 05}
0xAD4BE One Of Option: 1400, Value (16 bit): 0x578 {09 08 A6 11 01 01 78 05}
0xAD4C6 One Of Option: 1600, Value (16 bit): 0x640 {09 08 A7 11 01 01 40 06}
0xAD4CE One Of Option: 1800, Value (16 bit): 0x708 {09 08 A8 11 01 01 08 07}
0xAD4D6 One Of Option: 1867, Value (16 bit): 0x74B {09 08 A9 11 01 01 4B 07}
0xAD4DE One Of Option: 2000, Value (16 bit): 0x7D0 {09 08 AA 11 01 01 D0 07}
0xAD4E6 One Of Option: 2133, Value (16 bit): 0x855 {09 08 AB 11 01 01 55 08}
0xAD4EE One Of Option: 2200, Value (16 bit): 0x898 {09 08 AC 11 01 01 98 08}
0xAD4F6 One Of Option: 2400, Value (16 bit): 0x960 (default) {09 08 AD 11 31 01 60 09}
0xAD4FE One Of Option: 2600, Value (16 bit): 0xA28 {09 08 AE 11 01 01 28 0A}
0xAD506 One Of Option: 2667, Value (16 bit): 0xA6B {09 08 AF 11 01 01 6B 0A}
0xAD50E One Of Option: 2800, Value (16 bit): 0xAF0 {09 08 B0 11 01 01 F0 0A}
0xAD516 One Of Option: 2933, Value (16 bit): 0xB75 {09 08 B1 11 01 01 75 0B}
0xAD51E One Of Option: 3000, Value (16 bit): 0xBB8 {09 08 B2 11 01 01 B8 0B}
0xAD526 One Of Option: 3200, Value (16 bit): 0xC80 {09 08 B3 11 01 01 80 0C}
0xAD52E One Of Option: 3400, Value (16 bit): 0xD48 {09 08 B4 11 01 01 48 0D}
0xAD536 One Of Option: 3467, Value (16 bit): 0xD8B {09 08 B5 11 01 01 8B 0D}
0xAD53E One Of Option: 3600, Value (16 bit): 0xE10 {09 08 B6 11 01 01 10 0E}
0xAD546 One Of Option: 3733, Value (16 bit): 0xE95 {09 08 B7 11 01 01 95 0E}
0xAD54E One Of Option: 3800, Value (16 bit): 0xED8 {09 08 B8 11 01 01 D8 0E}
0xAD556 One Of Option: 4000, Value (16 bit): 0xFA0 {09 08 B9 11 01 01 A0 0F}
0xAD55E One Of Option: 4200, Value (16 bit): 0x1068 {09 08 BA 11 01 01 68 10}
0xAD566 One Of Option: 4267, Value (16 bit): 0x10AB {09 08 BB 11 01 01 AB 10}
0xAD56E One Of Option: 4400, Value (16 bit): 0x1130 {09 08 BC 11 01 01 30 11}
0xAD576 One Of Option: 4533, Value (16 bit): 0x11B5 {09 08 BD 11 01 01 B5 11}
0xAD57E One Of Option: 4600, Value (16 bit): 0x11F8 {09 08 BE 11 01 01 F8 11}
0xAD586 One Of Option: 4800, Value (16 bit): 0x12C0 {09 08 BF 11 01 01 C0 12}
0xAD58E One Of Option: 5000, Value (16 bit): 0x1388 {09 08 C0 11 01 01 88 13}
0xAD596 One Of Option: 5067, Value (16 bit): 0x13CB {09 08 C1 11 01 01 CB 13}
0xAD59E One Of Option: 5200, Value (16 bit): 0x1450 {09 08 C2 11 01 01 50 14}
0xAD5A6 One Of Option: 5333, Value (16 bit): 0x14D5 {09 08 C3 11 01 01 D5 14}
0xAD5AE One Of Option: 5400, Value (16 bit): 0x1518 {09 08 C4 11 01 01 18 15}
0xAD5B6 One Of Option: 5600, Value (16 bit): 0x15E0 {09 08 C5 11 01 01 E0 15}
0xAD5BE One Of Option: 5800, Value (16 bit): 0x16A8 {09 08 C6 11 01 01 A8 16}
0xAD5C6 One Of Option: 5867, Value (16 bit): 0x16EB {09 08 C7 11 01 01 EB 16}
0xAD5CE One Of Option: 6000, Value (16 bit): 0x1770 {09 08 C8 11 01 01 70 17}
0xAD5D6 One Of Option: 6133, Value (16 bit): 0x17F5 {09 08 C9 11 01 01 F5 17}
0xAD5DE One Of Option: 6200, Value (16 bit): 0x1838 {09 08 CA 11 01 01 38 18}

I found this EFI shell grub-mod-setup_var on github
so i would need to make USB and boot from it then write

usage like this:
setup_var_cv nameOfVarStore offsetInVarStore [optional variable size] [optional value to write]
so in my case:

setup_var_cv SaSetup 0x147 0x2 0xA6B
for 2666 to unlock

and now I want to ask
what are the risks of editing bios vars? can CMOS reset fix it if something wrong happens?