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?