I would like to note that that you need multibeast 4.3 in order to find the ati driver needed for\This could probably work for other Y560 models too. I don't know but maybe. Try using other settings for "busratio=XX" maybe it helps.
I manged to install a clean vanilla Snow Leopard 10.6.7 using original 10.6.3 restore disk from my other MacBook. I got everything working AND ethernet. Graphics acceleration, QE/CI working, sound working, wifi & bluethoot working etc. (you get the idea )
Here is the link for the drivers & apps I used and the working Ethernet kexts:
old link removed
I also used iBoot and MultiBeast (latest version), an 10.6.3 original ISO, 2 USB Memory Drives one of 16GB and a smaller one and for setup preparation in windows TransMac (google it).
iBoot and MultiBeast you can get them from tonymacx86 but you have to register there to download them.
I have the IdeaPad Y560 i7 model which dosen't have Graphic Switching => no Intel & ATI Graphics, only ATI 5730M
Setup Preparation in Windows:
Installed TransMac and formated the 16GB drive with the 10.6.3 ISO (right click in Transmac on drive - format using image/ISO)
Then i formated the smaller drive with the iBoot ISO also using TransMac.
Because my HDD wasn't formated in GUID partioning type but MBR the setup wouldn't recognize my partiton and allow installing on it.
So i had to use a modified setup. The files are included in the archive I uploaded. I copied them overwriting the ones on the 16GB drive using TransMac (for this you should check the "Show hidden files" option in TransMac)
I downloaded the 10.6.7 Combo Update from Apple and burned it on a DVD.
Restart and boot from the small iBoot USB drive and select from the iBoot menu the 16GB drive.
If it restarts try using busratio=XX flags. For my i7 i used "busratio=17".
Start setup, format partiton, select packages and start installation.
After installation finishes boot using iBoot USB drive.
Run 10.6.7 Combo Update BUT DO, I REPEAT DO NOT restart when it finishes.
Install MultiBeast with the following selected:
-Drivers & Bootloaders -> Kexts & Enablers -> Graphics -> ATI 184.108.40.206 Drivers
-Customizations -> System Definitions -> MacBook Pro -> MacBookPro 8.1
Run "Kext Helper b7" from archive and install all the kexts included in archive. Pay attention to USB\IOUSBFamily.kext and PS2 folder for they are very important because if you restart you will loose all usb, mouse, trackpad and keyboard functionality if they don't install.
Run "Kext Utility" and wait a few minutes to finish.
Restart and if you don't have any problems .....Voila
I would also like to thanks vlad.s