The rom that I present below is taken directly from the roms kitchen by xdadevelopers, the one that is for me and for many, the best Android research and development forum. The Vanilla Rootbox v3.0 Rom It is valid for both the GT-I9100 model and the GT-I9100P, and it is made from the source code itself with some additions of Cyanogenmod, AOKP y ParanoidAndroid. The ideology of this rom is simplicity and lightness, so it does not have any additions and the correct applications have been respected for a correct operation of the terminal. In this new version of the rom you gain in response speed and in better battery consumption, although there are still the problems of playing video in high resolution or HD format, as well as other small bugs typical of the roms of Cyanogenmod and AOKPIf you need more information about the rom you can go through the official thread of it. 
Requirements to install the rom
We must have a Samsung Galaxy S2, model GT-I9100 o GT-I9100P, which must also be rooted and with Clokworkmod Recovery installed, the battery should be charged at 100 x 100 and usb debugging enabled from the settings menu of the terminal to be flashed. Once all this is verified, we download the rom for the I9100 or for the I9100P, plus the Google Gapps and copy them without decompressing in the root of the sdcard, then we reboot in Recovery Modeand we will proceed to the installation of the rom.
Rom installation method
Already from recovery-modewe will do the following:
- Wipe data factory reset
- Wipe cache partition
- Advanced / wipe dalvik cache
- Go Back
- Mounts and storage and we format System
- Go Back
- Install zip from sdcard
- Choose zip from sdcard
- We select the zip of the rom and install it
- Choose zip from sdcard
- We select the zip of the Gapps and install them
- Reboot system now
With this we will have the vanilla rom at their version 3.0 correctly installed in our terminal. More information - RootBox Rom Jelly Bean 4.1.2 for Samsung Galaxy S2, How to root Samsung Galaxy S2 Download - Rom GT-I9100, Rom GT-I9100P, Gapps
I haven't tried it yet, has anyone? the basis is from JB?
The operation is excellent, I'm already in 3.2
I just updated it ... it had 2.9 ... I'll leave my comments ... 2.9 does not present any problem
it works excellent !! : D ...
Azrael 99
Do you have problems playing HD videos? How long does the battery last?
I have a problem with the SD card, it does not recognize it.
I also have a problem with the battery, when it is turned on and connected to the charger it says: charging, but the charge percentage keeps dropping!?!? I do not know what to do?
have you solved that problem?
Excuse me, the card does not recognize me, help me with this problem please
I got version 3.3 through goo.im. The problem is that I do not know where it is updated and how I have to do it. Thanks
Hello I have a question which is the google gaps is the one that I have to download, help is that I am new to this
I already solved the issue of the gapps the issue is that this rom does not have a radio