I Have a Shuttle AV49VN Mainboard with a VIA Chipset and onboard AC97 sound, the sound does work, BUT the actual sound quality is very poor and blotchy, can i fix this and how?

Verify that your vendor/device ids are in the kexts.

Use the Appendix of this guide to help you find the 4 numbers you need: http://forum.insanelymac.com/index.php?showtopic=18642

The first set of numbers in the form of 0x + (device id) + (vendor id) go into this file: /System/Library/Extensions/AppleAC97Audio.kext/Contents/PlugIns/AppleAC97AudioVIA.kext/Contents/Info.plist

This file already has 0x30591106. Based on your audio drivers from Shuttle, you could also have 0x30581106.

The second set of numbers in the form of 0x + (device id) + (vendor id) go into this file under the ICH2 section: /System/Library/Extensions/AppleAC97Audio.kext/Contents/PlugIns/AppleAC97AudioIntelICH.kext/Contents/Info.plist

This file already has 0x24458086 and 0x24358086. Based on your audio drivers from Shuttle, you could also have: 0x24158086 or 0x24258086 or 0x24C58086

But use Windows -> Device Manager to verify.

well winodws device manager said it was
PCI\VEN_1106&DEV_3059&SUBSYS_A2371297&REV_50\3&13C0B0C5&0&8D
which i presume means
0x30591106