I have created a boot cd that should work perfectly for a P8P67 Pro although it may also work for other Sandy Bridge motherboards.
What you will need..
1 - My freshly prepared boot CD AndyBoot CD Image
1 - Boot from your newly burnt AndyBoot CD
2 - Swap the boot CD for your Installation DVD or USB Boot Drive, wait a few minutes then press F5
3 - Select your install DVD or USB drive and hit return (no kernel flags should be required)
4 - Go through the usual installation routine
5 - Once install is complete reboot using the boot CD
6 - Hopefully you are now at the desktop with a working internet connection so go ahead and install all available OS X updates and reboot using the boot CD.
7 - Back at the desktop (hopefully) with an up to date system you can now browse the boot CD in the Extras Folder you will find a 'Post Install' folder containing #####, An ATI Graphics Update and a new kext for the AL892 audio chipset. Run ##### and select the following options..
8 - copy the mach_kernel that you downloaded to the root of your Snow Leopard boot drive.
9 - Reboot again - this time you shouldn't need the boot CD
10 - Once back at the desktop return to the Extras/Post Install folder and install the newer ALC892Enabler.pkg for better sound support.
11 - If you use a recent ATI graphics card run the ATI Graphics Update package from the extra/post install folder
12 - Reboot and hopefully you are done!
Ok I decided that was all far too complicated so now it's even simpler.
1 - Download the bootcd
2 - Boot from it
3 - Install Snow Leopard from DVD or USB Installation media
4 - Reboot using the bootcd
5 - Install 10.6.7 update combo (if you forgot to download it first no problem, just run the install package from the cd and reboot to get a working internet connection then go ahead and download it).
6 - Once the update is complete reboot again using the bootcd
7 - Open the bootcd, copy the installer package to your desktop and then run it (it's important to copy the installer to disk and not run it from the cd otherwise your sound will not work - this a bug in the postinstall script that I haven't been able to track down yet.
8 - Reboot without the bootcd.
Job done and everything should be working
The package will install the new kernel, the sandy bridge friendly chameleon boot loader and all of the relevant kext's for this motherboard. Additionally it installs all of the new ATI kexts providing native 5800 and 6800 support.
I have tested the bootcd pretty extensively by formatting my own Snow Leopard install and rebuilding it from scratch using only this bootcd and the original snow leopard install DVD so I am pretty confident that it works.
Enjoy and please feel free to provide feedback.