most of the time after driving and coming to a stop the idle will hang up arround 2000rpm then drop to idle. It seems to do it more once its heats right up the idle will hang at 2000rpm for ever it sparatic though sometimes it will return to idle. No ammount of throttle jabbing helps and this happens on both gas and petrol, once when i closed the hood the idle increased (the air cleaner rubs the hood becuase of lpg ring). Would this appear to be a vaccum leak of some sort, maybe carbi base or the joint between the lpg ring??