I'm having issues with my power brakes on my Barracuda. Factory disc in front and drum in back. Everything is new. Bench bled the master dot 5 used. Bled all four corners until brake pedal was hard. Now I start the car and the pedal pressure drops almost 3/4 down. Could that mean I don't have enough vaccum or the booster is bad? Cam is a Lunati 703. The motor has 15-16 of vaccum at idle.