don't listen to savage. he's an idiot. YOu can't use a modified retail bios because of at least two reasons.
#1 the modified retail bioses use a different rc4 key than the debug unit so it can't even decrypt it.
#2 the debug kits use an unencrypted eeprom and the retail bioses try to decrypt the eeprom on boot. Since there's nothing to decrypt, the bios will fail at the flubber screen.
(I've gotten this far, hopefully all I have to do is put an encrypted 1.0 eeprom in my xbox and it will work.)
As far as I know I'm the only one working on this so until I complete it or get some help then you're sol. (Unless you can edit counter-strike's xbe) It not only needs to be patched to debug but it also needs a debug path to an exe. If those flags are met it should boot no prob in your debug kit.)
If you can edit this debug path I'd appreciate it very much if you'd inform me on how to do it as I'm working very hard to hack my debug kit. Get in touch with me in private and we'll discuss things further.