MacBook Pro late 2011 AMD GPU disable I´ve done what's explained on "GPU problem - Boot Hangs on Grey Screen" question.

In the option "about this Mac" only appear the Intel HD. The graphics card status app shows "i".

I searched for the amdradeon3000 kext on finder, and its in the folder I've created for backup on single user mode. 

It seams to have worked, but it only boot correctly after a few power cycles to a black screen. Before it would show random graphics colours and glitches, or a grey or blue screen.

Using find command on user mode the amdradeonx3000.kext appears in 2 locations:
- .../extensions-off
and
- .../.pkinstallsandboxmanager-systemsoftware/nrsandletters.orphanedsandbox/root/system/library/extensions/amdradeonx3000.kext.

It is possible that this last one is causing the black screen at boot?

Should I move it to another folder?
It is possible that this last one is causing the black screen at boot? - I don't know yet. With verbose mode enable at some point it appears a message relating the reboot to a kernel panic.

Should I move it to another folder? - I've moved it. Don't know if it effects the boot sequence, but the behavior got regular.

Boot to a black screen, press power button to shutdown. Repeat 4 or 5 times. When the message about the panic shows, the boot process runs successfully.