The EFI string in com.apple.Boot.plist will only normally include your Video and Ethernet so if you have built a DSDT to include Video & Ethernet then you can remove...
As for your audio, I have only tested here with ALC888 so as your moob uses ALC889A all I can suggest is you have a read of tmongkol's thread to double check specifics.
As I got through my speedsteps the voltage and frequency increments are still the same with 10.5.8 but I have actually noticed a 2-3 Deg increase in temp at idle (Worth noting though London is quite hot this weekend - It's actually NOT raining ~) the Fan could be running at lower RPM or CPU could be pulling more current - ameter GUI anyone?
I'll be interested too if anybody has higher temps, as then I have to question is VoodooPower worth using?
For me so far, it is doing a good thing though