An update,here: I just restored all the kexts I moved back into the extension folder amnd now the Sonnet card is working again. It is definitly using some of the apple kexts as it installs on Pwermac G5 with no driver CD or download driver from Sonnet's website. So I am back to a working card but still have slow boots and periodic thrashing in the sys logs as it keeps searching for the dead onboard hardware again.
Sonnet strikes again. I never had luck with their combo cards.
Seems odd that PCI is pulling all the kexts. Likely only one or two, but which? PCI IO is a whole different set of kexts.......
Did you try the Terminal method to kill onboard FW?
Sonnet support got back to me. Their reply is that the card's support depends on two drivers:
AppleFWOHCI.kext Apple Driver IOFireWireFamily.kext/Contents/PlugIns
So I guess I can try putting all the others into the diasabled folder and see if that stops the fruitless searching timing out issue.