Gran Turismo 2 did not have much luck on the 1.1 prototype hardware, 2.x PCB hardware will have much better compatibility due to great improvements in the hardware!
Please remember that this a prototype device and does likely not reflect what the final hardware will be like. This includes compatibility with games as well.
You can hit up ps-io.com if you have any questions since I am but a mere tester, I do not understand the technology behind this wonderful invention.
PSIO Hardware Version: 1.1
PSIO Software Version: 1.1A
All tested on an SCPH-5502 with a missing CD deck.