Hi there, long time reader, first time poster (or almost) 
Seems I have a problem upgrading emunand on a 3DS, let me explain:
Had a 5.1 3DS, no gateway or compatible DS flashcard (gateway is on the way, that's why I want to "prepare" this console)
✓ Downgraded to 4.5 using the browser exploit + gateway 3.03 launcher.dat + gateway.dg for my region (EU)
✓ Return to gateway launcher, format EmuNAND
✓ Boot EmuNAND (classic mode, as I have no gateway flashcard right now), confirmed I'm on GW3D 4.5
✓ Format system while in EmuNAND (this is to have a different ID than my NAND for eshop etc...)
✓ Reconfigure system (time/date/nick/network ...) in EmuNAND
✓ Update system while in EmuNAND --> takes a while and tells me the upgrade has succeeded and ask to reboot
✓ Reboot (in SysNAND) and access the gateway menu via web browser exploit
X Boot classic mode -->> BSOD, then I can only reboot to SysNAND obviously.
I've tried many times, with 2 different SD Card, the 2GB that came with the 3DS, and a 32GB, no success, I can't boot into Classic mode after EmuNAND upgrade.
Isn't 3.03 supposed to be compatible with 9.4 EmuNAND ? Or maybe I missed something else, I've read a lot, but I'm pretty new at 3DS tinkering.
Thanks !
edit:
OK, I found the reason, you can't boot into EmuNAND 8.x or higher without a gateway red card in the slot, hence it doesn't work after upgrade.
Seems I have a problem upgrading emunand on a 3DS, let me explain:
Had a 5.1 3DS, no gateway or compatible DS flashcard (gateway is on the way, that's why I want to "prepare" this console)
✓ Downgraded to 4.5 using the browser exploit + gateway 3.03 launcher.dat + gateway.dg for my region (EU)
✓ Return to gateway launcher, format EmuNAND
✓ Boot EmuNAND (classic mode, as I have no gateway flashcard right now), confirmed I'm on GW3D 4.5
✓ Format system while in EmuNAND (this is to have a different ID than my NAND for eshop etc...)
✓ Reconfigure system (time/date/nick/network ...) in EmuNAND
✓ Update system while in EmuNAND --> takes a while and tells me the upgrade has succeeded and ask to reboot
✓ Reboot (in SysNAND) and access the gateway menu via web browser exploit
X Boot classic mode -->> BSOD, then I can only reboot to SysNAND obviously.
I've tried many times, with 2 different SD Card, the 2GB that came with the 3DS, and a 32GB, no success, I can't boot into Classic mode after EmuNAND upgrade.
Isn't 3.03 supposed to be compatible with 9.4 EmuNAND ? Or maybe I missed something else, I've read a lot, but I'm pretty new at 3DS tinkering.
Thanks !
edit:
OK, I found the reason, you can't boot into EmuNAND 8.x or higher without a gateway red card in the slot, hence it doesn't work after upgrade.