If you are linking 2 PS2's all you need is one i-Link/firewire, 4 pin to 4 pin (the i-link/Firewire port on the PS2 is 4 pin) and two copies of the game you are wanting, ie GT 3.

If you want 3 - 6 PS2's linked up you need a i-Link/Firewire hub, the hubs use 6 pin plugs and usually have 6 ports. Thus the i-Link/Firewire cables you would need are 4 pin to 6 pin. The 4 pin ends into the PS2 port and the 6 pin ends into the Hub ports.

Hook it all up with the power off on all PS2 units, then fire it up you should be good to go. If you have any more questions PM me.

PS. i-Link and Firewire cable are the same you can use either or, i-Link is just Sonys special name for the same product.