There is supposed to be a vacuum line from the regulator to the large black hose that connects the air cleaner to the valve cover. There is a small connection at the valve cover side. It's purpose is to provide the fuel an escape route if the diaphram in the regulator fails. Without it, gas will spill on the engine. I'm not sure if you can buy the rubber nipple in the regular. You may want to give Phil a call. If you cannot buy it separate, send me a PM and 'll tell you about a temporary fix.