You must remove the cold start valve. Then with it set to discharge into a container, have someone turn on the ignition. With the ignition on, the fuel pump will pressure up the system, and you should not see any flow out of the cold start valve. If fuel dribbles out, you need to replace the valve. This valve is controlled by a thermoswitch that allows it to pulse for only a few seconds on a cold start. When the engine is warm, the cold start should not operate at all. Cost of a new valve is about $75.
On the topic of vacuum leaks........have you checked the intake seal? As I recall from your last note, it appeared as though you might have changed out the engine recently. If so, and you swapped out the accessories, you may have a vacuum leak at the intake manifold to block interface. You can test this with the car running with a soapy solution.