Since this is the technical assistance thread:
My mod chipped Japanese Dreamcast plays every game, except for San Francisco Rush 2049 which I just bought. It gets to the "produced or dev'd by SEGA..." and then kicks back to the system menu. I tried a boot disc, which got the game to a black screen after the "produced or dev'd by SEGA...", VMU displayed the game logo, but no game started up.
Then, hoping it wasn't a laser problem, I tried about 5 other games (Japanese, euro, US, indie, burned), and all played flawlessly. Then I tried SFR2049 in my other Dreamcast (standard US model), it played perfectly on VGA and RCA booting up every time.
So I've concluded that for some odd reason, SFR2049 just does not work on a Japanese modded Dreamcast. Not a laser problem or scratched disc, just an oddity.