restoring my 70 vette and had a vacume problem for a long time, wiper door and headlights, i replaced every thing that had to do with vacume leak. not to much help out there so i tried tried and tried again. after about 2 months go by and going crazy and hearing that im not the only one out there i decited to vacume test 1 vacume line at a time and found 1 small brand new hose under dash did not hold vacume and helped and i was looking at the brand new pull down switches 1 for headlights and 1 for wiper door and got rid of the metal connters and those stupid connters and took each hose and put them right into the valve ,guess what happend,NO VACUME LEAK. THE complete system works GREAT. so if your wiper door or head lights give you problems or vacum leaks get rid of those stupid connters at the pull down switch 
