I have the same machine, and did the very same processor upgrade, and mine is working fine. What version of OS X are you running? I'm running Mavericks (10.9.4).
10.9.4 here as well, though the issue cropped up in 10.7 once I put in the new processors.
I was already running Mavericks before I did my processor upgrade. I used Tiamo's replacement boot.efi to install Mavericks. Did you use Chameleon to install Mavericks, or Tiamo's replacement boot.efi?
What exactly does it do? KP or does nothing? Did you perform clean install or upgrade? I had once similar issue with one customer's 1,1 before and after CPU upgrade. It turned out to be HDD/corrupted filesystem issue. Replacing HDD with new one + clean install cured the problem.
If it does KP, post the KP log.