Nah, I thought about this : Hopper > detector pipe > item box > Split into several pipes using the new + pipe, then several valves to different boxes. First box won't output by default. When I drop item into hopper, it goes through the first item box, and get scanned at the same time. Now since I scanned the item i know what it is, and I can open the corresponding valve (I guess i can use the gates to differenciate items right ?), and let the item exit the first box. When the item has passed the valve, there is another detector just behind used to close the valve.