Zeiger is right, here are my current boot flags... my card is in the first slot, however im still running 0311 BIOS, so I cant promise it will work...
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>EthernetBuiltIn</key>
<string>Yes</string>
<key>GraphicsEnabler</key>
<string>No</string>
<key>Kernel</key>
<string>mach_kernel</string>
<key>Kernel Flags</key>
<string>darkwake=0 npci=0x3000</string>
<key>Legacy Logo</key>
<string>Yes</string>
<key>Timeout</key>
<string>2</string>
<key>UseKernelCache</key>
<string>Yes</string>
<key>Graphics Mode</key>
<string>"2560x1440x32"</string>
</dict>
</plist>
Best
John