vacuum leak at brake?

[rwb22]

I have a 2005 Escape and have heard on occasion a vacuum leak coming from under the dash on the drivers side. I have recently noticed that when I use the brake that it stops while I'm pressing on the brake pedal. I am assuming that somehow the leak is in the brake booster and coming through to the inside. Or could this leak be something else and just happens to stop when I press on the brake? Do I have to have the booster replace or is there a "rebuild" kit of some sort?
Also, I've been getting such a difference in mpg and wonder if I could plug the vac line to the booster and drive it to see if this is the cause of the bad mpg?

[i_a_n112784]

Yes, it's your booster leaking. There is no rebuild kit, it needs to be replaced. As far as plugging the vacuum line, that is dangerous because you will have no power brakes, and it is hard to say if that little bit of a vacuum leak will cause a drop in mpg.