Brake booster vacume pump.

How low is your vacuum? I believe your cam is not overly radical? I ran PB's down to 9"s of idle vacuum before on limited use cars. With deceleration, it would build enough vac to stop decently. The only issue I had was with stop and go traffic, or repeated pumping of the pedal. I will admit that full, daily driver type performance was lacking, but with the price of electric vac pumps, I just learned to live with it.