Start by unplugging the network cable and watching it - if it wakes with the network cable disconnected, then it is being woken by an internal process, if it doesn't, then it's being woken by external access.
If it's an internal process, disable funplug (rename the script) and observe, if it wakes, it's being woken bu the OEM firmware, if it doesn't, it's a funplug process - consult the funplug people.
If it's an OEM firmware process, disable ALL the servers and observe - it should not wake - re-enable each server, one by one, and you should find which one is the cause.