With the formalities out of the way, let’s get started. Before you begin, make sure you’ve the following files at the ready:
Step 1: Download the AdyScorpiusMIUIv2.1-ICS-i9100-2.1.20.zip via this link. The file is over 100MB, so may take a few moments for those on slower connections.
Step 2: Once the download is complete, copy the .zip file to /sdcard.
Step 3: Boot your Galaxy SII into Recovery Mode.
Step 4: Select Wipe Data/Factory Reset, and then go to Mounts and Storage and select Wipe System.
Step 5: Install zip from sdcard – Version 2.1.
Step 6: Wipe Data/Factory Reset once more.
Step 7: Reboot your device, and you should be good to go.