This is a problem that occurs on and off, but has been happening more frequently. After I step on the break and let off there is a vacuume leak type sound, like its sucking air. If I tap the brake hard, it will stop. I had a guy tell me that it was probably a diaphram in there that has ruptured. I have no idea. If you have a guess let me know, and do you think that it is causing a loss of power? Thanks for your help.