Thanks for the script, Artur. At the end, the generated SSDT is quite similar to the multishit's suggested SSDTs.
Also patched AICPUPM, but still not much luck getting sleep working as well as more than one or two states. In most of the tests, I only get 1.6 in HWMonitor, some combinations get me 3.3 also, but nothing in between.
Oh well, anyway, thanks again. I guess this is the SSDT to keep, although I still have those "P-State stepper error"s.
Oh yeah, btw, I also had the exact problems that 2 guys had along this thread: a KP mentioning AICPUPM and the ACPI plugin. I got them when trying to solve the stepper errors I have permanently. My only solution was to bring the SMBIOS to MacPro3,1. Of course, I didn't try all of the possibilities, but so far, this is the only one now which allows me to boot into the system (after patching AICPUPM, generating SSDT and some things more, probably). And I also am guessing that MacPro3,1 in some way messes the steps.
What bothers me is that I see guys all the time using other SMBIOS. Oh well, time will tell.