I have a 1992 F350 7.3 IDI. I am having brake issues where the pedal is on the floor and if I pump it, it will go up, but then fades. I was told the vacuum pump may be bad. I bought one and installed it (under the alternator), but my truck has a second vacuum pump near the top front of the motor. Most people don't know about this second pump. Where can I get one. Even my ford shop manuals don't show it. My truck was made in late 1991. I understand there is a difference on those made before March 1992 and those made after March 1992. Thanks for any help.