I have a 2002 Protege, the brakes work fine, the booster seems to work fine, there are no noticeable vacuum related isses on the car, but mostly in morning when cold can hear an air leak. When brake pedal is depressed the leak can no longer be heard. I cannot hear the leak or find any obviouse leak in the engine compartment. When I get down under steering I can manually stop the leak by pressing on rubber boot that surrounds the plunger behind the brake pedal that goes through the firewall. The brakes and booster seem to function fine, any ideas what is causing this leak noise and how to fix it? Thanks, Dan