2001 Ford Escape hissing noise at brake pedal?

I have a audible hissing noise coming from the brake pedal. Not sure if it's positive or negative pressure. Brakes work fine. When I tap on the brake pedal, the noise goes away. When I tap on the pedal again, the noise come back. The engine also has a rough start when it's cold outside, but once the engine is warmed up it runs fine. I had the fuel filter replaced and the spark plugs and intake seals have also been replaced as well. Could these (2) seperate issues be related?

Thanks in advance!
~Ron