As we know R4 team has stopped updating old R4 firmware. They too busy with R4 sdhc. But worry no more, because now you can use homebrew firmware base on YSMENU. Basically, the firmware much alike R4 firmware, only that you dont need to patch unplayable new game or doing arm7 fix anymore..
the one i got here already packed with latest working cheatcode ( even the one that didnt work in R4 FW) up to oct 2008! Feel free to download and see for yourself. To install, just remove all R4 files (excluding the roms folder of course!) in the card root and replace with the extracted file .
R4 Latest Firmware
EDIT: Link Updated!