I checked the vacuum as you advised. It stops hissing when I go ahead and plug the vacuum hose after removing off the brake booster. I will be placing the brake booster on order at Autozone. Once, I go ahead and replace I will get back to you with a staus update. I am fairly confident that this will resolve the issue once and for all. is there anything you can tell me about removing the booster? Anything you might know? Thanks a million!