GT4 never had true online racing allowing you to race with others in real time. GTPlanet hosts plenty of fun "online" events where users send in their times for comparison with others and call it a race.
Xlink works on ps3 if you set up the modem like you would a ps2. This means taking the network adapter start-up disk and creating a profile on the virtual memory card. The rest sets up like you would a ps2.
