Ford Repair: Scratching Sound When I press Brake Deeply, ford mustang, brake booster

Question
Dennis,

I have a 2001 Ford Mustang.

When I press the brake pedal almost all the way in I hear a scratching sound like two surfaces rubbing together.  The sound comes from inside of the car near my feet and legs.  I only hear the sound when I push the pedal in deeply.

My theory is that the piece of metal that suspends the pedal is rubbing against another part of the car.  What do you think?  Is there a name for this problem?  Any thoughts on what might need to be replaced or lubricated?

By the way, I had my brakes done about 10k miles ago, so I'm pretty sure I don't need new pads.  Plus it definitely doesn't seem like the sound is coming from anywhere other than near my feet and legs.  

Thanks in advance for your help,
Steven


Answer
I am unable to diagnose noises thru the internet. Sorry.
You might be hearing the vacuum in the brake booster, some vehicles will make a hissing noise from the booster if the pedal is forced down. Does this happen when braking or just when you force the pedal?