Quarterhorse636

im not blowin but I put a boost gauge in my car to be able to watch my vacuum. ill start my car and it will stay at 14hg or so then when I hit a red light and sit for a couple minutes it will drop to 10hg and stay there until I turn the car off and back on and then it will go back up to 14 hg till I hit the next red light. what would cause the vacuum to drop so dramatically and suddenly? a diaphragm that uses the vacuum opening maybe?

88 orangepeel notch

Fox/SN tech section please