Hi! I have a early 2011 macbook pro with a failed AMD GPU and I'm trying to fix it following the instructions of that MacRumors thread. However I'm in a dead end trying to resetting the PRAM. I need it in order to reset the startup disk and make the laptop boot from OSX which has been installed in the SSD using a macbook air. I can't reset the PRAM because a few years ago I set a firmware password. It seems that this is preventing the cmd + alt + p + r combo keys working. At the same time I can't boot into recovery or Sierra because it hangs while booting due to the faling gpu. Also I can't boot into single user mode because before pressing cmd + s I have to choose the startup disk with alt and to my knowledge and tries, pressing the cmd + s combo after clicking in the startup partition I want to boot from isn't working. Any idea or suggestion? Thanks in advance for your support.