I have two 69 Camaros. One z28 and one SS L78 both power disc brake cars. Both have have the boosters replaced and brakes rebuilt by po. The Z has an almost touchy brake feel while the SS has a hard pedal almost like it would with the engine not running. The vacuum is 14 or so at idle, the booster holds vac but it takes serious pedal pressure to stop. I am thinking booster but would like to hear you guys input. I also have replaced the vac valve on the booster as this caused a similar problem on my GTO.