Brake Booster Blues

Yep, when the booster goes bad you get a vacuum leak every time you hit the brakes. My dad was pulling his hair out, replacing everything on an 5.0 EFI swapped 82 GT. It would surge badly because the EFI couldn't control the leak. I found it when he was driving it, everything was fine then he came to a stop with his foot on the brakes, as soon as he let off the Idle surge would stop. Press the brakes and surge again. New booster, surge gone.