I am not aware of any bug fixes beyond 2.11 either. The things I remember those updates consisted of are mainly measures that prevent hybriding, the removal of the XXXXXXX, the X2010 JP Flag Color, and the hidden performance parts, and then the very last update, allowing you to keep your DLC after the servers shut down. You really aren't missing much at all by staying on 2.11; if anything, those updates took a lot more away.
The 5G was never removed; it was the JP Flag Color and the XXXXXXX that got removed.