@Aurola
Hervé is right. You'll need to set the DVMT and CFG Lock.
For my 7040 MT, I had both cfg lock and DVMT pre-alloc set with the following commands respectively using modgrubshell.efi
setup_var 0xAF 0x0
setup_var 0x350 0x4
After the changes, disable the following in config file
framebuffer-fbmem
framebuffer-stolenmem