First at all, I already know that my english is very bad, I hope you can understand this.
I managed to get the audio exploit to run whatever .xbe, I explain it:
First you must install the exploit without any change, insert a Audio CD, execute linux.xbe, etc.
Now, you need to transfer the ST.DB that you have copied to the XBox before, to the PC (the file should have changed).
With this file, replace the following bytes (starting at position 0xFF):
"05 14 00 00 00 89 85 72 01 00 00"
with these
"81 76 FF 14 01 00 10 90 90 90 90"
Copy this modified file to the XBox (yes, again), and overwrite the old file.
Now, you can sign any .xbe with the habibi key using "xbedump file.xbe -habibi" and copy out.xbe as linux.xbe in E: and the .xbe will run.
And I must recognize that the guy that made the audio exploit is very clever, he put some nice protections to avoid running other .xbe than linux.xbe
This method was tested on a XBox v1.0, with kernel 4034 and dashboard 4920, I don't know if it will work in other XBoxes