This patch is now required for online play.
Make sure you have the following:
1) A 3DS with Mario Kart 7 game inserted.
2) A WiFi connection
3) Nintendo E-Shop
Go to Nintendo E-Shop and at the bottom should be a Mario Kart 7 Icon. Tap on it, and initiate a download for this patch. Once installed, you can play online. This patch does the following:
Eliminates Spawn Glitches on Maka Wuhu, Wuhu Loop, and Bowser's Castle 2.
To uninstall this patch, Go to your 3DS Settings and go to Data Management. However, uninstalling this will no longer allow you to play online. You can reinstall this patch to play online again.
Enjoy Glitch-free Mario Kart 7. ^_^