As many are finding, people who have bought their G2 recently are having colorful lines whenever you try to turn on your screen when on KitKat Roms. This method fixes that (with this ROM only).
This is for people who are currently running the latest firmware (D80120A_00). I assume it'll also work with newer updates, but I can't make any promises.
As we've all seen, IORoot does not work on 4.4.2 on Tmobile devices for some reason. To get around that, we need to downgrade our devices to stock firmware. We will be following hyelton's guide, and lrwjr1964's discovery.
--Downgrade to 4.2.2--
First, navigate to hyelton's guide. Download the 4.2.2 stock firmware, from his link. On his Storage Cow site, navigate to the TMobile G2 folder, and then download the D80120C_00.kdz file. This is our stock firmware that we will be flashing to our device. You will also need to navigate to the link to the R&D Flash tool. The file is the LGMOBILEAX file. Install the LG Mobile Support tool. Launch the tool.
Next, we will be using lrwjr1964's discovery (post 2902 in the same thread). Plug in your phone, install any drivers needed, and let it get connected. Once you're all good to go, click 'options' in the top right hand corner, and then 'upgrade recovery'. What this will do, is download the latest D80120A_00.kdz file, and install it to your phone. How the program works, is it downloads the file to your computer, then transfers the file and flashes it. What we are going to do, is interrupt that process, insert our .kdz, and let it flash for us. Pretty nifty, huh?
You'll want to watch it super closely as it downloads. As soon as it finishes, yank the usb out of your phone. (I've done this twice without consequence. I don't make any guarantees, though.) This interrupts the file transfer, and throws you an error screen. Navigate to the folder "C:\ProgramData\LGMOBILEAX' . ProgramData is a hidden folder, so you'll need to make hidden folders visible. Rename your D80120C file exactly to what the file name of the other file is. Then, copy it over. Once it's finished, replug in your phone, let it connect, and let it resume the process. When it finishes, your phone will be running 4.2.2. How sweet is that?
Now, this should work just as you're used to if you've done this before. Autoprime explains how to do this really well, so take a look at his thread here
Again, if you've done this before, you're right at home. If not, WACOMalt has a thread you should check out here Make sure you download the correct .img for your phone. The Tmobile one. There's many different methods of flashing TWRP, but using the app Flashify worked easiest for me. It's on the Google Play store, and makes flashing it a cinch.
--Install KitKat and Re-Root--
This is one step you want to be careful with. Mess this one up, and you could be back at page one. SmiLey497 has the stock rom here. Ensure you not only snag the rom itself but get the SU file in the 'attached files' section.
Copy both files onto your phone, and boot to TWRP. You can do this easily from within the Flashify app.
Within TWRP, you need to do a standard wipe. After that, flash the ROM file first, and then the SU file after. DO NOT reboot your phone in between the files. If you do, you'll have just flashed the rom you had two hours ago when you began, and still not have SU. Once you do have them both flashed, reboot your phone and you're done.
Congrats!! Your phone should now be running 4.4.2, and you should have root access. Go have some fun. Watch some Community, go for a jog, take a nap, eat dinner...do something FUN! You've earned it.
I hope this guide is helpful. It very possibly could not work for you, or even mess up your phone. As far as I know, only myself and lrwjr1964 has used this method. I have very limited developing knowledge, so I likely won't be able to help with any too technical problems. Still, I'll be around to help as I can.
If this works for you, comment to let others know.
The best of luck!