in your guide you forgot that we need to backup AppleACPIPlatform.kext and IOPCIfamily.kext before the combo update (10.6.8), and then replace the new ones with the olders.
This is necessary to avoid the PCI error @reboot.
I think if you do step 11 after applying the 10.6.8 update, you won't get the error. I found out the hard way too. I did it twice, once at step 11 and then once after the 10.6.8 update.
Has anyone with the l502x got the nvidia card working? I installed the tonymac 2.0 update. It seems that there is something in the system profiler, but it looks a little incomplete.
PCIe Lane Width: x16
Vendor: NVIDIA (0x10de)
Device ID: 0x0df5
Revision ID: 0x00a1
If i boot with GraphicsEnabler=yes, I get an error and a stalled boot.