Brakes in a 1997 Bonneville

Hi, I have a `97 pontiac bonneville. Not super-charged, I was having really tight brakes, like the bakes you have when the engine is off but youre being towed, any-ways I replaced the font brakes because they needed it. Still really tight and you could hear a vacuum leak.I replaced the brake booster, that the master-cylinder is connected to and the vacuum sound was greatly toned down. BUT my brakes are still. Very very hard. To the point of being concerned for family. PLEASE HELP. Thank you for youre time on this matter.