[Galaxy S II Android Development] Roxxors:
Tried this on my phone

My phone had become so unbearably slow I was about to toss it in the garbage, but then I saw this thread. I thought "hell, if there's any chance my phone will be back to how it was when it came out, I'll happily risk killing it". For reference, I also have the VYL00M "insane" eMMC chip, fwrev 0x19.

I'm coming from NeatROM 4.1.2, and let me tell you something, after installing C11 M9 with this kernel, my phone is FLYING. Whether it's TRIM, the improvements in KitKat, the improvements in ART (yes I am using ART and it works perfectly!), or the cumulative effect of them all, my phone feels brand new, everything is faster, snappier and better!

Even if there is a chance this might yet brick my phone (very doubtful), I still couldn't care less. My phone feels amazing.

Here's the steps I took to transition from NeatROM 4.1.2 for anyone else looking to install this, I also re-partitioned data to 6GB and system to 1GB in order to have more TRIMable free space as well as more space for apps generally. These steps might not be the optimal way to do it but it worked for me so I'm sharing it, and I believe this'll work for any 4.1.2 and higher ROM's. As always, I am not responsible for any damage to your phone, so try these at your own risk.

[Update: streamlined the process a bit]

[Update 2: used Lanchon's fixed .pit file, updated stuff to M12 including Lanchon's newest TRIM kernel that also fixes FPBug. If you want a different M release or nightlies, you'll have to roll your own Odin flashable kernel following these instructions]

Step 1: Backups, backups, backups. This could brick your phone (but probably almost definitely not as explained by OP, a backup is still wise however) and it will definitely delete all 16GB of your internal SD card (also known as USB storage) due to repartitioning, so remember to backup your music, your photos and your contacts in addition to a nandroid backup.

Important: make an EFS backup too, if things go wrong and you lose your EFS partition without backup, your phone is toast. I used kTool from the Play Store to do my EFS backup. Remember to save all of your backups off of your phone (the external SD card works too, just be careful not to accidentally format, to be safe also make a copy on your PC)

Step 2: Download C11 M12 from here: http://download.cyanogenmod.org/?type=snapshot&device=i9100. Put it on your external SD card.

Step 3: Put your phone into download mode (home button + vol down), then plug your phone into your computer and open Odin3 1.85.

Step 4: Grab the attached Odin files, put the .pit file in PIT and the tar.md5 file in PDA. Press start and wait [Note: I had some issues with Odin, just keep trying, it worked for me even when it said it failed.]

Step 5: Boot your phone into recovery (home button + vol up), and flash the full C11 M12 ROM (this is the zip file you put on the SD card earlier). Now you should be able to boot into C11 M12 for the first time! Go to settings>storage and format the internal SD card so that it shows up again.

[Note: if your storage doesn't show up with this, go into recovery again -> mounts and storage -> format sdcard0. Try to see if it works even if it says it failed. If it still doesn't work: connect to your PC, select "mount USB storage", and format the drive through Windows.]

Step 6: Follow the steps in OP to flash the TRIMable kernel from this thread and install LagFix, then run LagFix to TRIM system, data and cache.

Optional: Enable ART by enabling developer options (in settings>about phone tap the build number 7 times to enable dev options) then scrolling all the way down.

Hope it works as well for you as it did for me!