6490m 6750m driver switch Macbook Pro Early 2011

Hi all, I have a Macbook Pro Early 2011, I've had the Discrete Graphics problem, where the AMD Chip got too hot and desoldered from the main board making the computer useless. I reballed the chip myself before Apple issued the Repair Extension Program for this issue. So it is fixed now no need for the Repair Program.

At first I had to move the AMD Kext files from the System/Library/Extensions folder in order to start the MBP with the integrated chip only, so I could access the MBP. This was before the reball. When I did the reball I moved back the Kext files to their places, and started using the AMD chip, but instead of using the 6750m driver as it is the one this computer has, it automatically chose the 6490m, which it is fine as the computer is working alright but it is not using all its power, minor graphic glitches almost imperceptible, I can live with them.

So I did a clean reinstall of the OS, still the OS uses 6490m driver, then upgraded to Yosemite, still using the 6490m driver. Is there a way to manually choose the 6750m driver?

Thank you!