Hi ginnza,

Playing DSi ROMs is not yet possible, and will probably never be possible as they are working on the 3DS now instead of working on the DSi. The Acekard2i hasn't got a firmware update for the new 3DS Firmware so it won't work on the newest firmware. You might be better off buying a SuperCard DSTWO or an R4iDSN (from r4idsn.com) which are working on the latest 3DS firmware and are constantly updated.

I hope this helps.