Sounds like the valve is only partially open or the rubber washer inside it is loose in which case it would need a new one. This would apply to your new valve, kitchen faucet, or the valves that you shut off to repair the kitchen pipes. Old gate valves that have been there forever have the rubber on the valve stem get hard. One day, you close it and then upon reopening, the rubber pulls loose from the stem and gets stuck in the path of the water restricting its flow. Or maybe they put in a cheaper valve that isn't a full port valve. I see a lot of the home centers carrying ball valves where the opening inside isn't a full port. Post back with what you find. Depending upon what valves you closed to start with, try to isolate it between hot and cold.