OK guys here are the symptoms; I'm driving down the road, and go to pull of the interstate & stop to realize that I can push my brake pedal in about 2" further then it usually goes, and it is soft on top of that. well I check fluid etc., and don't find any problems. here is the interesting part - when the vehicle is turned off (i.e. no vaccum) then if feels a lot closer to normal. what should I replace.