You can try this for ethernet & Audio (i´m using my gfx string for 7600gt this example is for Alc889a(ID (8086,293e), Ethernet realtek 8119b)

This works with ALCxxx (AppleHDA.kext & Alcinject.kext) audio based, with Alc850 it´s not necessary.

1. Copy gfxutil & 7600gt.hst to your desktop

2. Open up Terminal & change directory to your desktop
cd /Desktop

3. Rename 7600gt.hst to 7600gt.hex
mv 7600gt.hst 7600gt.hex

4. Convert hex file to property list file
./gfxutil -s -n -i hex -o xml ./7600gt.hex ./7600gt.plist

5. Find the device path for "ethernet"
./gfxutil -f ethernet
Example output: DevicePath = PciRoot(0x1)/Pci(0x1c,0x5)/Pci(0x0,0x0)

6. Edit 7600gt.plist with Textedit, adding the following lines:
<key>PciRoot(0x1))/Pci(0x1c,0x5)/Pci(0x0,0x0)</key>
<dict>
<key>built-in</key>
<string>0x01</string>
</dict>
Note: replace the device path with yours

7. Convert plist file to hex file
./gfxutil -i xml -o hex ./7600gt.plist ./7600gt.hex

8. Copy the string in the new 7600gt.hex to /Library/Preferences/SystemConfiguration/com.apple.Boot.plist

9. Replace /System/Library/Extensions/IONetworkingFamily.kext with the vanilla one & repair permissions

10. Reboot

11. Repeat steps 5 to 9 for ALC899A fix
11.1 Find the device path:

./gfxutil -f pci8086,293e (remember the device ID)
11.2 Edit 7600gt.plist & add:
<key>PciRoot(0x1)/Pci(0x1b,0x0)</key>
<dict>
<key>PinConfigurations</key>
<data>
</data>
<key>built-in</key>
<string>0x00</string>
<key>layout-id</key>
<string>0x0000000c</string>
</dict>
11.3 Remove /System/Library/Extensions/ALCinject.kext

How to find device ID go here

or you can use this

more info in Netkas forum

credits to Eclau, Macmatrics, Time ed....