Madshrimps informs is that
The Inquirer spotted a modification of the X1800GTO which unlocks 4 pipelines and allows you to bump the performance to X1800XL level,
"CHINESE website HKEPC shows us how to mod a X1800GTO to a X1800XL by enabling the 16 pipelines. a HIS card was used. You can download the appropriate mod document and the mod bios. Of course, everything you will do to your machine will be at your own risk. "
HKEPC tester also included a few benchmark runs with 3DMark comparing the performance before/after the modification, a quick and dirty chart of his results I threw together here.