EX4i DS System Software 1.43, Update -> Website claims the fix for 1.4.3 was implemented "EX4DS supports NDSi V1.4.3 firmware. 2011-06-30"
I have not tried it on DSI XL (note: I was unable to get the prior ex4i version 1.42 working on DSIxl v1.4.3)
:download: Download from source
Firmware...