Found this in mph's forum
I have tested this on Mega Man Maverick Hunters X and GTA. It works perfect on Mega Man, but on GTA it is sometimes glitchy (walls dissapear, sound quits).
You basically replace the folder
MS0://MPHGameLoader/flash0/kd with the folder
from the 2.50 firmware files and the folder
from the 2.00 firmware files.
Sleep mode in GTA seems to work better if you pause it first.