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.....Yes, I believe air is being sucked into the booster when I turn the engine off. Since air should not pass through the back of the booster, the booster is probably bad. Not sure how or why at this point.



The air inlet into the booster is at the rear of the booster around the pushrod. When you press the brake pedal air is admitted into the rear half of the booster. But it shouldn't be leaking when the brakes are released. Just a question, are you sure the booster pushrod is fully extended with the pedal at rest? You see what I'm getting at?

"We live in a time when intelligent people are being silenced so that stupid people won't be offended".