Vacuum Hose Leak
Listen for a whistleing/sucking sound under your hood. Look for cracked or disconnected small rubber hose. Spray some carb cleaner at any suspected sites(while it's running), if there is a change in rpm's you've found something.
Another way to find is to use an "UNLIT" propane torch to give litte extra fuel to enrichen the mix. Change in RPM. Check one hose at a time. Also chack the mating surfaces of the intake manifold as well.


