Check out my thread over in the T-Mobile M8 forums by clicking the link below. Instructions and downloads are there.
Please post in the T-Mobile thread so I don't have to keep track of multiple threads.
You absolutely need S-Off!! The AC WiFi is listed. I don't list WiFi bands because there are too many to fit on screen. RAM is DDR2. When I have the time I'll make a 16GB variation for your specific device if you have S-Off
Also, please post your comments/questions in the T-Mobile thread to help me out. Thanks.